SUMMARY
Characters get removed for no reason.
I've experienced this issue a lot for some time now.
Finally I can reproduce:


STEPS TO REPRODUCE
1. Create a new document (tab indent, size 4)
2. Create a non empy line first
2. On the next line insert at least one tab and then a word, for example 123456
3. Move cursor to first column in front of the tabs and press enter

Example:
"Line 1\n
\t123456"

OBSERVED RESULT
"Line 1\n
\n
456"

EXPECTED RESULT
"Line 1\n
\n
\t123456"

Having multiple tabs removes even more characters after the tabs.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux with KDE
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.105.0
Qt Version: 5.15.9

ADDITIONAL INFORMATION
X11, Nvidia-proprietary