SUMMARY
***
NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols.
See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
***
When typing, there is suggested text.  I would select this and continue.  But, when I would bace to a word, it would arbitrarily add a suggested text, without being requested to do so.

STEPS TO REPRODUCE
1. type some words
2. use the suggested words to fill in one or more words (auto-completion)
3. backspace to an auto-completed word, and obseve it randomly insert an additional word in (this additional word often being one of the previous words that auto-complete had previously been called upon to insert).

OBSERVED RESULT

When typing in kwrite, I was taking notes from a site (https://www.chiark.greenend.org.uk/~sgtatham/bugs.html) on writing proper bug reports.  I had written the following:

[quote]
Bug reports

Describe WHAT did, then WHAT happened.  Tell them what you saw 

[/quote]

I was using the text prompts for the last three words ("what", "you", "saw").  I ended up one space away from the word "saw", which was the end of the sentence.  So, I backspaced one space to add a period, but as the cursor got beside the word "saw", that word was immediately repeated and inserted into the document.  Thus, I ended up with the following:

[quote]
Bug reports

Describe WHAT did, then WHAT happened.  Tell them what you sawsaw.
[/quote]

I attempted to go back, but yet again it inserted a couple of words, this time "say" and then "yo".  Thus, I ended up with the following at this point:

[quote]
Bug reports

Describe WHAT did, then WHAT happened.  Tell them what you sawsayyo
[/quote]

I pressed the backspace key four times, and then it inserted "wha":
[quote]
Bug reports

Describe WHAT did, then WHAT happened.  Tell them what you sawswha
[/quote]


Here is what I saw:
The window with the text.  The lines are numbered 1 ("Bug reports"), 2 (*blank*), 3 ("Describe WHAT you did, the WHAT"), 3 continued (an arrow indicating a wrapping of line #3) ("happened.  Tell them what you"), 3 continued again (an arrow indicating a wrapping of the line) ("sawswha")

On the bottom, under the window with the written text, I see:

[quote]
3:71  INSERT  en_GB  Soft Tabs: 4  UTF-8  Normal
[/quote]

Note, the word "Normal" above is in a box.  Also note, regarding "INSERT", I have tested this when "OVERWRITE" is chosen, and I get the same overzealous word insertion behaviour from the program.

Beneath that is the suggested text, which currently shows:

[quote]
wha  what  whatever  whatsoever
[/quote]

"wha" is highlighted.

Finally, underneath, I see the digital keyboard.

EXPECTED RESULT
So, upon the cursor meeting the last word ("saw") when I backspaced one space to insert the period, I expected that it would NOT continue to insert words, and instead would allow me to insert the period and continue.  This would have given me the following:

[expectation]

Bug reports

Describe WHAT did, then WHAT happened.  Tell them what you saw.
[/expectation]

As mentioned, the expectation above did not happen.  There were no error messages.  The program kept inserting these suggestions, in spite of me not having chosen the suggestions. 



SOFTWARE/OS VERSIONS

Linux/KDE Plasma:    5.19.9-1-MANJARO-ARM
(available in About System)
KDE Plasma Version:  5.25.5
KDE Frameworks Version: 5.98
Qt Version: 5.15.6

ADDITIONAL INFORMATION
OS type:  64-bit
Pinephone Pro
Processors:  4 x ARM Cortex-A53, 2 x ARM Cortex-A72
Memory:  3.8 GiB of RAM