SUMMARY
I use archlinux, kate 20.08.0, Qt 5.15, plasma 5.19.

Randomly the contextual menu doesn't display inside a tab of kate (text zone), when I do a right mouse click.

To get a contextual menu I have to open a second tab, and then do a right mouse click, then the contextual menu is then possible on the first tab.

I didn't manage to get the exact conditions for triggering the bug, but it can occur when there is a single tab inside kate, and after editing/pasting text, saving a document inside a single tab, randomly the right mouse click doesn't bring the contextual menu.

It's not a hardware problem (mouse) because at the same time I can use the right mouse click in other applications (firefox, libreoffice).


STEPS TO REPRODUCE
- Install kate 20.08.0
- Install Qt 5.15
- Use plasma 5.19
- open kate, edit/past/save text on the single tab
- try to do a right mouse click on the single tab --> randomly it will not work

OBSERVED RESULT
no contextual menu when doing a right mouse click

EXPECTED RESULT
a contextual menu should occur,
a workaround is to open a second tab, and do a right mouse click in the second tab,
after this action the contextual menu is possible on the first tab


SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: archlinux 64 bits, plasma 5.19
(available in About System)
KDE Plasma Version: 5.19
KDE Frameworks Version: 5.73
Qt Version: 5.15
Kate version : 20.08