Created attachment 178985 [details]
Shows making new panel and doing everything to reproduce it

SUMMARY
Spacer makes widgets overlap each other if you slide it over icons-only task manager, making it not removable.

STEPS TO REPRODUCE
1. Open edit mode
2. Add spacer, flexible or not
3. Slide it over icons-only task manager or system tray, or other way around

OBSERVED RESULT
Spacer goes behind any widget after that and you can puts widgets over it, makes them overlap each other

EXPECTED RESULT
Spacer stays with cursor and doesn't make other widgets overlap each other, making them unusable afterwards

SOFTWARE/OS VERSIONS
Operating System: EndeavourOS 
KDE Plasma Version: 6.3.2
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.13.4-arch1-1 (64-bit)
Graphics Platform: Wayland

ADDITIONAL INFORMATION
System is freshly installed, global theme and window decorations is Nothing, Icons are Fluent, everything else(colors, applications etc) is Breeze. Size of panel doesn't make spacer reachable, neither does removing all widgets over it (sometimes it does), nvidia-open-dkms driver with RTX 4050, changed to nvidia only on laptop.