SUMMARY In a dual monitor setup, the windows maximized on the second monitor are moved to the primary monitor when the second monitor goes off and goes on again. The windows that are not maximized on the second monitor or any windows in the first monitor are not affected. They remain where it are supposed to be. In general, the monitors goes off as result of the automatic lock screen followed by a long period (15min) of inactivity, but it happens manually. I mean, turn the second monitor off by the monitor switch and turn it on again after a short period (seconds). STEPS TO REPRODUCE 1. In a dual monitor setup, place windows on the first and second monitor. Then maximize some windows, specially on the second monitor. 2. Turn the second monitor off by pressing its power off switch. 3. Wait a few seconds. Turn the second monitor on again. You see the maximized windows placed on the second monitor to show up on the first monitor. OBSERVED RESULT The maximized windows placed on the second monitor are showed now on the first monitor. The maximized windows on the first monitor are not affected. Any non maximized window in any monitor are not affected. EXPECTED RESULT Any windows must stay in its the original place. SOFTWARE/OS VERSIONS Operating System: openSUSE Tumbleweed 20210220 KDE Plasma Version: 5.21.0 KDE Frameworks Version: 5.79.0 Qt Version: 5.15.2 Kernel Version: 5.10.16-1-default OS Type: 64-bit Graphics Platform: X11 Processors: 8 × Intel® Core™ i7-3770 CPU @ 3.40GHz Memory: 14.6 GiB of RAM Graphics Processor: GeForce GTX 970/PCIe/SSE2 ADDITIONAL INFORMATION This bug happens since KDE 5.20 at least. Its not new on KDE 5.21.
This bug was fixed somehow and it does not manifest itself anymore, probably it was fixed in some iteration of kde 5.21 updates. My system, currently is running: Operating System: openSUSE Tumbleweed 20210330 KDE Plasma Version: 5.21.3 KDE Frameworks Version: 5.80.0 Qt Version: 5.15.2 Kernel Version: 5.11.6-1-default OS Type: 64-bit Graphics Platform: X11 Processors: 8 × Intel® Core™ i7-3770 CPU @ 3.40GHz Memory: 14.6 GiB of RAM Graphics Processor: GeForce GTX 970/PCIe/SSE2