SUMMARY
After a tooltip for a table cell is shown, slowly moving the mouse inside them causes the tooltip to flicker. A workaround is to disable the Morphing Popups desktop effect (found in this issue: https://bugs.kde.org/show_bug.cgi?id=416531).

STEPS TO REPRODUCE
Either:
1. Open KSysGuard
Or:
1. Open System Settings
1a. Select the Systemd section

2. Hover over a table cell until its tooltip appears
3. Move the mouse quickly inside the row and notice that the tooltip does not flicker and only changes position when the mouse stops moving
4. Move the mouse slowly inside the row
5. Move the mouse one row downwards (or a column over for KSysGuard) and repeat steps 3 and 4

OBSERVED RESULT
When moving the mouse inside the first row slowly, the tooltip follows the mouse closely and quickly appears and disappears.
When moving the mouse inside the second row (or column for KSysGuard) slowly, the tooltip follows the mouse closely but may either flicker or have its text flicker with the text of the previously-shown tooltip; the font size will be scaled up or down so that the size of the tooltip does not change.

EXPECTED RESULT
The tooltips do not flicker and their text contents remain constant while inside a single table cell

SOFTWARE/OS VERSIONS
Operating System: Manjaro Linux
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.85.0
Qt Version: 5.15.2
Kernel Version: 5.13.15-1-MANJARO (64-bit)
Graphics Platform: X11

ADDITIONAL INFORMATION
I'm not sure if this bug is specific to tables. I haven't found any other places where this issue occurs during normal usage.