My external monitor is located above my notebook monitor. Notebook is configured main screen. External monitor is frequently docked and undocked (each time I leave my desk and take the notebook with me for a meeting). When windows were left on secondary screen before disconnecting and the same secondary screen is then reconnected, the windows are restored to that secondary screen, but they are all lined up at the same y-location (close to bottom of screen) and their window height is squashed to zero.
Thanks for the report Norbert, I've just tested this on Plasma 5.20.2 and cannot reproduce the issue. Can you please test and confirm if this issue is still occurring or if this bug report can be marked as resolved, thanks.
Sorry, I don't have the computer or setup any more. Just drop the issue - it is not worth any further investigation after this long time.
Thanks for the update Norbert. If you do find the bug affecting you again in the future don't hesitate to open a new bug report.