Created attachment 150364 [details]
flickering panels

SUMMARY
Panels sometimes have motion/flickering and sometimes don't auto-hide (if set to.)

STEPS TO REPRODUCE
1. Setup two or three monitors and set some panels auto-hide.
2. Open/use many programs.
3. Do many things and wait, maybe hours.

OBSERVED RESULT
Panels sometimes have motion/flickering and sometimes don't auto-hide (if set to,) shown (top and right-side panels auto-hide) in attached video (large size so short time so you should probably loop.)  Some minimized programs flicker (most/all web browsers, as if having fast activity) on their taskbar section's lower area for a while, or even continually appear & disappear (HexChat) for a while, though haven't likely seen official KDE programs do either.  With this setup, depending how one uses/selects programs (even excluding HexChat) an entire panel may flicker fast, like it's being redrawn too much (often if I selected a right-side lower screen program, top screen panel flickers fast, but different setups might react differently.)

If displays idle then blank, sometimes 4K's panel moves (leaving desktop that was below) about 25% to the right and its right-side section moves onto part the 1080p screen (as sometimes still happens with programs snapped into the 4K right-side, which the latter is probably Xinerama but I never set panels to span after trying once years ago in a now-gone KDE installation.)

EXPECTED RESULT
Always auto-hide panels set to do so.  Optionally don't show fast updates in panel for minimized programs.  When screens blank, don't move things (panels, general programs, and under heavy background usage, also desktop icons.)

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Slackware64 15.1-current / 5.25.2
KDE Plasma Version: 5.25.2
KDE Frameworks Version: 5.95.0
Qt Version: 5.15.4

ADDITIONAL INFORMATION
Since I have 4K, 1600x1200, 1080p screens, don't think I had enough time to prove top (for file managers/Dolphin) & right-side monitors (for xterms/Konsole) are auto-hide, but setting these two up like that is always something I do (past five years) in first 24hrs setting up KDE with this monitor setup (and this KDE installation has been used since past Winter.)  Luckily auto-hide panel doesn't appear over Konsole when maximized on right, but does appear over file managers maximized at top, sometimes for a long time.

For attached video, almost 6/32 threads were left (6787.17 GFlops each according to bogomips, maybe 5% usage each) and 7GB RAM, with no audible activity on HDD (which has /home/user/.kde) and main KDE is on SSD/M2/NVME.  I doubt problem is scant CPU resources, as some 2010s PCs run KDE Neon User 5.25 fine with two threads (typically using few programs, though all mine were idle besides aforementioned networking, SimpleScreenRecorder, a few daemons past  first page of results in commands like top (atop, htop, btop.))