Yeah, I got that, too, with the current master state, very strange...

works here (latest kate master, old ktexteditor)

(In reply to Waqar Ahmed from comment #2)
> works here (latest kate master, old ktexteditor)

what do you mean?
I noticed that kwrite doesn't have this bug.

I noticed also that as other use this bug disappear...

renaming katerc as katerc.bak kate the bug is solved.  
This is its content:

[Audio Preview Settings]
Autoplay=false

[ColorPicker]
HexLengths=3,6,9,12
NamedColors=false
PreviewAfterColor=true

[General]
Allow Tab Scrolling=true
Auto Hide Tabs=false
Close After Last=false
Close documents with window=true
Days Meta Infos=30
Diagnostics Limit=12000
Diff Show Style=0
Elide Tab Text=false
Expand Tabs=false
Icon size for left and right sidebar buttons=32
Last Session=de Lubac e la Dei Verbum
Modified Notification=false
Mouse back button action=0
Mouse forward button action=0
Open New Tab To The Right Of Current=false
Output History Limit=100
Recent File List Entry Count=10
Restore Window Configuration=true
SDI Mode=false
Save Meta Infos=true
Session Manager Sort Column=0
Session Manager Sort Order=0
Show Full Path in Title=false
Show Menu Bar=true
Show Status Bar=true
Show Symbol In Navigation Bar=true
Show Tab Bar=true
Show Tabs Close Button=true
Show Url Nav Bar=true
Show output view for message type=1
Show text for left and right sidebar=false
Show welcome view for new window=true
Startup Session=new
Stash new unsaved files=true
Stash unsaved file changes=false
Sync section size with tab positions=false
Tab Double Click New Document=true
Tab Middle Click Close Document=true
Tabbar Tab Limit=0

[KPropertiesDialog]
1920x1080 screen: Height=498
1920x1080 screen: Width=407

[KTextEditor Document]
Allow End of Line Detection=true
Auto Detect Indent=true
Auto Reload If State Is In Version Control=true
Auto Save=false
Auto Save Interval=0
Auto Save On Focus Out=false
BOM=false
Backup Local=false
Backup Prefix=
Backup Remote=false
Backup Suffix=~
Camel Cursor=true
Encoding=UTF-8
End of Line=0
Indent On Backspace=true
Indent On Tab=true
Indent On Text Paste=false
Indentation Mode=normal
Indentation Width=4
Keep Extra Spaces=false
Line Length Limit=10000
Newline at End of File=true
On-The-Fly Spellcheck=true
Overwrite Mode=false
PageUp/PageDown Moves Cursor=false
Remove Spaces=1
ReplaceTabsDyn=true
Show Spaces=1
Show Tabs=true
Smart Home=true
Swap Directory=
Swap File Mode=1
Swap Sync Interval=15
Tab Handling=2
Tab Width=4
Trailing Marker Size=1
Word Wrap=false
Word Wrap Column=80

[KTextEditor Editor]
Encoding Prober Type=1
Fallback Encoding=ISO 8859-15

[KTextEditor Renderer]
Animate Bracket Matching=false
Auto Color Theme Selection=true
Color Theme=Breeze Light
Font=Hack,10,-1,7,50,0,0,0,0,0
Line Height Multiplier=1
Show Indentation Lines=false
Show Whole Bracket Expression=false
Text Font=Hack,10,-1,7,400,0,0,0,0,0,0,0,0,0,0,1
Word Wrap Marker=false

[KTextEditor View]
Allow Mark Menu=true
Auto Brackets=false
Auto Center Lines=0
Auto Completion=true
Auto Completion Preselect First Entry=false
Backspace Remove Composed Characters=false
Bookmark Menu Sorting=0
Bracket Match Preview=false
Chars To Enclose Selection=<>(){}[]
Default Mark Type=1
Dynamic Word Wrap=true
Dynamic Word Wrap Align Indent=80
Dynamic Word Wrap At Static Marker=false
Dynamic Word Wrap Indicators=1
Dynamic Wrap not at word boundaries=false
Enable Accessibility=true
Enable Tab completion=false
Enter To Insert Completion=true
Fold First Line=false
Folding Bar=true
Folding Preview=true
Icon Bar=false
Input Mode=0
Keyword Completion=true
Line Modification=true
Line Numbers=true
Max Clipboard History Entries=20
Maximum Search History Size=100
Mouse Paste At Cursor Position=false
Multiple Cursor Modifier=134217728
Persistent Selection=false
Scroll Bar Marks=false
Scroll Bar Mini Map All=true
Scroll Bar Mini Map Width=60
Scroll Bar MiniMap=true
Scroll Bar Preview=true
Scroll Past End=false
Search/Replace Flags=140
Shoe Line Ending Type in Statusbar=false
Show Documentation With Completion=true
Show File Encoding=true
Show Focus Frame Around Editor=true
Show Folding Icons On Hover Only=true
Show Line Count=false
Show Scrollbars=0
Show Statusbar Dictionary=true
Show Statusbar Highlighting Mode=true
Show Statusbar Input Mode=true
Show Statusbar Line Column=true
Show Statusbar Tab Settings=true
Show Word Count=false
Smart Copy Cut=true
Statusbar Line Column Compact Mode=true
Text Drag And Drop=true
User Sets Of Chars To Enclose Selection=<>(){}[]
Vi Input Mode Steal Keys=false
Vi Relative Line Numbers=false
Word Completion=true
Word Completion Minimal Word Length=3
Word Completion Remove Tail=true

[KTextEditor::Search]
Replace History=,lanng=grc" class="greco",class="greco",span,#menu,ul#menu,#828282,#flip-navigation\\, .flip-navigation,\\\\n ,\\\\n    ,/span>,<span lang,     <li>,",h3,b>,i>,</p>,</p>\\\\n,<p>\\\\1.  ,’, class="min gray",Iria. Data:,min gray,h4>,li>,h5,h5>, , sé ,',h2>,\\,,\\\\",convert,convert_bin,p>,href="<?php echo "$culturanuova/" ?>filosofia/,.opere,#opere,<?php echo $more ?>,más,più,Sepa más,/ 11 /,/ 10 /,/ 09 /,/ 05 /,h3>,browsers,</Menuname>,</Name>
Search History=blockquote,lettore,cfr,<span class="c23">, class="western",font face="Symbol",moralismo,</span>, align="justify",<span class="(.*?)">,face="Athenian",face="Symbol",font,font-style: normal,#,toolt,h1,blockquo,boxino ,img ,  position: relative;\n  z-index: 3;,ins ,&shy;,aggiunta,td.nobordo,#nav,#menu,.menu,ul#nav,.desktop,.desk,#piede,cambialingua,#giardinetto,#giardinetto\\, ,flip-navigation,#BBB6AE,flip,#flip-navigation,\\\\n,absolute,news,/p>,<p lang, <li>,  <li>,\\\\",calc,stellari,h3,.inline, class="fl",h4,strong>,em>,<span>,</li>\n\n</ol>,\\\\</l\\\\i>\\\\n\\\\n\\\\</ol\\\\>,<\\\\/li>\\\\n\\\\n<\\\\/ol>,</li>\\\\n\\\\n</ol>,<ol start='(.*?)' >\\\\n<li>,&#39;,tridentino, class="text_texto_3",&#160;,Iria</p>\n <p>Data:,text_textop_3,h3>, class="text_subtitulo_2"><br /, class="content-layout-collapse-title text_subtitulo_1",  <div class="content-layout-collapse-body">,<div class="content-editable">,<t,  <table border="0" cellpadding="0" cellspacing="0" class="content-layout">,  </table>,   </tbody>,    </tr>,     </td>,     <td>,    <tr>,   <tbody>,  <table border="0" cellpadding="0" cellspacing="0" class="content-layout content-layout-collapse">,intl,;extension=php_intl,h5>,Uccello,p>,subtitle,</dd>,<dd>,dt>,&nbsp;, sè ,protezionismo,</p>,<p>,<td class='andr'>(.*?)</td>,<td class='andr alt'>(.*?)</td>,-,\\,\s

[KateSQLPlugin]
SaveConnections=true

[KateSQLPlugin][OutputCustomization][blob]
backgroundColor=202,199,191
font=Noto Sans,10,-1,0,50,0,0,0,0,0
foregroundColor=0,0,0

[KateSQLPlugin][OutputCustomization][bool]
backgroundColor=202,199,191
font=Noto Sans,10,-1,0,50,0,0,0,0,0
foregroundColor=0,0,0

[KateSQLPlugin][OutputCustomization][datetime]
backgroundColor=202,199,191
font=Noto Sans,10,-1,0,50,0,0,0,0,0
foregroundColor=0,0,0

[KateSQLPlugin][OutputCustomization][null]
backgroundColor=202,199,191
font=Noto Sans,10,-1,0,50,0,0,0,0,0
foregroundColor=0,0,0

[KateSQLPlugin][OutputCustomization][number]
backgroundColor=202,199,191
font=Noto Sans,10,-1,0,50,0,0,0,0,0
foregroundColor=0,0,0

[KateSQLPlugin][OutputCustomization][text]
backgroundColor=202,199,191
font=Noto Sans,10,-1,0,50,0,0,0,0,0
foregroundColor=0,0,0

[Konsole]
AutoSyncronize=true
AutoSyncronizeMode=0
KonsoleEscKeyBehaviour=true
KonsoleEscKeyExceptions=vi,vim,nvim,git
RemoveExtension=false
RunPrefix=
SetEditor=false

[MainWindow]
1920x1080 screen: Height=660
1920x1080 screen: Width=1277

[PluginSymbolViewer]
ExpandTree=false
SortSymbols=false
TreeView=false
ViewTypes=false

[Printing][HeaderFooter]
FooterBackground=211,211,211
FooterBackgroundEnabled=false
FooterEnabled=true
FooterForeground=0,0,0
FooterFormatCenter=
FooterFormatLeft=
FooterFormatRight=%U
HeaderBackground=211,211,211
HeaderBackgroundEnabled=false
HeaderEnabled=true
HeaderFooterFont=Hack,10,-1,7,50,0,0,0,0,0
HeaderForeground=0,0,0
HeaderFormatCenter=%f
HeaderFormatLeft=%y
HeaderFormatRight=%p

[Printing][Layout]
BackgroundColorEnabled=false
BoxColor=invalid
BoxEnabled=false
BoxMargin=6
BoxWidth=1
ColorScheme=Printing
Font=Hack,10,-1,7,50,0,0,0,0,0

[Printing][Text]
DontPrintFoldedCode=true
Legend=false
LineNumbers=false

[Shortcut Schemes]
Current Scheme=

[Shortcuts]
goto_next_diagnostic=none
goto_prev_diagnostic=none
hamburgerBar=none
kate_mdi_focus_toolview_Debug View=none
kate_mdi_focus_toolview_Locals and Stack=none
kate_mdi_focus_toolview_diagnostics=none
kate_mdi_focus_toolview_kate_plugin_katesearch=none
kate_mdi_focus_toolview_kate_plugin_symbolviewer=none
kate_mdi_focus_toolview_kate_private_plugin_katefileselectorplugin=none
kate_mdi_focus_toolview_kate_private_plugin_katefiletreeplugin=none
kate_mdi_focus_toolview_kate_private_plugin_katekonsoleplugin=none
kate_mdi_focus_toolview_kate_private_plugin_katesnippetsplugin=none
kate_mdi_focus_toolview_kateproject=none
kate_mdi_focus_toolview_kateprojectgit=none
kate_mdi_focus_toolview_kateprojectinfo=none
kate_mdi_focus_toolview_ktexteditorpreviewplugin=none
kate_mdi_focus_toolview_output=none
kate_mdi_hide_toolviews=none
kate_mdi_show_toolview_button_Debug View=none
kate_mdi_show_toolview_button_Locals and Stack=none
kate_mdi_show_toolview_button_diagnostics=none
kate_mdi_show_toolview_button_kate_plugin_katesearch=none
kate_mdi_show_toolview_button_kate_plugin_symbolviewer=none
kate_mdi_show_toolview_button_kate_private_plugin_katefileselectorplugin=none
kate_mdi_show_toolview_button_kate_private_plugin_katefiletreeplugin=none
kate_mdi_show_toolview_button_kate_private_plugin_katekonsoleplugin=none
kate_mdi_show_toolview_button_kate_private_plugin_katesnippetsplugin=none
kate_mdi_show_toolview_button_kateproject=none
kate_mdi_show_toolview_button_kateprojectgit=none
kate_mdi_show_toolview_button_kateprojectinfo=none
kate_mdi_show_toolview_button_ktexteditorpreviewplugin=none
kate_mdi_show_toolview_button_output=none
kate_mdi_sidebar_visibility=none
kate_mdi_toolview_Debug View=none
kate_mdi_toolview_Locals and Stack=none
kate_mdi_toolview_diagnostics=none
kate_mdi_toolview_kate_plugin_katesearch=none
kate_mdi_toolview_kate_plugin_symbolviewer=none
kate_mdi_toolview_kate_private_plugin_katefileselectorplugin=none
kate_mdi_toolview_kate_private_plugin_katefiletreeplugin=none
kate_mdi_toolview_kate_private_plugin_katekonsoleplugin=none
kate_mdi_toolview_kate_private_plugin_katesnippetsplugin=none
kate_mdi_toolview_kateproject=none
kate_mdi_toolview_kateprojectgit=none
kate_mdi_toolview_kateprojectinfo=none
kate_mdi_toolview_ktexteditorpreviewplugin=none
kate_mdi_toolview_output=none
mainToolBar=none

[Snippets]
enabledRepositories=/home/duns/.local/share/ktexteditor_snippets/data/Sirmione.xml,/home/duns/.local/share/ktexteditor_snippets/data/content-security-policy.xml,/home/duns/.local/share/ktexteditor_snippets/data/grafika.xml,/home/duns/.local/share/ktexteditor_snippets/data/greco.xml,/home/duns/.local/share/ktexteditor_snippets/data/htm5-semantikà.xml,/home/duns/.local/share/ktexteditor_snippets/data/incosmicon.xml,/home/duns/.local/share/ktexteditor_snippets/data/intell.xml,/home/duns/.local/share/ktexteditor_snippets/data/quiz.xml,/home/duns/.local/share/ktexteditor_snippets/data/scripts.xml,/home/duns/.local/share/ktexteditor_snippets/data/structured-data.xml,/home/duns/.local/share/ktexteditor_snippets/data/svg.xml,/home/duns/.local/share/ktexteditor_snippets/data/mio.xml

[Snippets][repository /home/duns/.local/share/ktexteditor_snippets/data/greco.xml]
shortcut Nous=
shortcut aletheia=
shortcut arché=
shortcut doxa=
shortcut eidola=
shortcut kalos-o-kindynos=
shortcut lang-grc=
shortcut lang-la=
shortcut sozein-ta-phainomena=

[Snippets][repository /home/duns/.local/share/ktexteditor_snippets/data/incosmicon.xml]
shortcut guarda-la-diretta=
shortcut modello-pagine-eventi=
shortcut multilingual=

[Snippets][repository /home/duns/.local/share/ktexteditor_snippets/data/mio.xml]
shortcut 11.da-un-lato-vert=
shortcut 111.d'altro-lato-vert=
shortcut 22.da-un-lato-orizz=
shortcut 222.d'altro-lato-orizz=
shortcut anchor=
shortcut blockquote=
shortcut break=
shortcut cliccabile=Alt+X
shortcut embed-audio=
shortcut embed-tag-wordpress=
shortcut embedde-foreign-div=
shortcut encoding=
shortcut footer=
shortcut header=
shortcut img-in-head=
shortcut ins-with-date=
shortcut php=
shortcut pro-biblio-mysql=
shortcut pro-etexts=
shortcut pro-filmografia-static=
shortcut pro-films-db=
shortcut pro-opere=
shortcut pro-opere-mysql=
shortcut shaped=
shortcut simbolo-menu(hamburger)=
shortcut summary-h2=
shortcut svg-arrow-condivisibile=
shortcut svg-drop-shadow=
shortcut svg-link-external-css=
shortcut temporized-text=
shortcut un-lista=
shortcut whatever-regex=

[Snippets][repository /home/duns/.local/share/ktexteditor_snippets/data/scripts.xml]
shortcut a-href=Ctrl+A
shortcut ahref=Ctrl+A
shortcut b=Ctrl+B
shortcut bash-head=
shortcut blockquote=Ctrl+Shift+B
shortcut bold=Alt+B
shortcut br=Ctrl+Return
shortcut cite=Alt+Shift+C
shortcut h1=Ctrl+1
shortcut h2=Ctrl+2
shortcut h3=Ctrl+3
shortcut h4=
shortcut hashtags-footer=
shortcut i=Ctrl+I
shortcut li=Ctrl+Shift+L
shortcut mente=Ctrl+Shift+M
shortcut p=Ctrl+P
shortcut p-subtitle=Ctrl+Shift+P
shortcut python3-head=
shortcut virgolette-finali=Alt+Right
shortcut virgolette-iniziali=Alt+Left
shortcut zione=Ctrl+Shift+Z
shortcut «=Alt+Shift+Left
shortcut ««=Alt+Shift+Left
shortcut »=Alt+Shift+Right

[debugplugin]
DAPConfiguration=

[filebrowser]
toolbar actions=back,up,forward,bookmarks,sync_dir,configure

[filetree]
editShade=183,220,246
listMode=false
middleClickToClose=false
shadingEnabled=true
showCloseButton=false
showFullPathOnRoots=false
showToolbar=true
sortRole=0
viewShade=211,190,222

How should I mark this bug? Solved? 
But something is happened (indeed someone else had the same problem) ...

(In reply to Duns from comment #6)
> How should I mark this bug? Solved? 
> But something is happened (indeed someone else had the same problem) ...

I think I saw this issue too at some point, but it kind of looked like it might actually be something related to display rendering. I don't recall the details what happened, but scrolling worked sporadically, I needed to switch tabs to have the edit view updated, and the typed text eventually was inserted, but did just not appear, as the edit area was not redrawn.

I had it not in the last days, but I am not sure it does really no longer happen, it can be an issue in all levels of the stack.

Can no longer reproduce that. Could you try with the latest updates of the whole system installed?