Created attachment 142464 [details]
Observed result

SUMMARY
Shown in the picture. I don't understand the issue clearly, but it's like this: I'm in Plasma Wayland session. I'm reading a feed in Kontact. I want to check updates using yay. I show & hide yakuake using the keyboard shortcut (Ctrl+backtick in my case). Kontact window has some letters on top of it (shown in red squares in the image).

STEPS TO REPRODUCE
1. Log in to plasma wayland session
2. Open Kontact
3. Go to feeds
4. Open a feed
5. Open yakuake using keyboard shortcut
6. Close yakuake using keyboard shortcut
7. Squares containing letters appear on top of the active feed

OBSERVED RESULT
See image

EXPECTED RESULT
Those shouldn't appear

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 5.14.11-arch1-1
(available in About System)
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
Reproducible only when Kontact is the previously active window, not when dolpin/kate/(put other KDE/Qt stuff) is the previously active window. Reproducible only using the keyboard shortcut, not by clicking on the yakuake logo in the system tray. Not reproducible in X11.