Created attachment 168708 [details]
bug-demonstration

SUMMARY
Resizing program opened in a maximized state results in the window to jump to a small size on its own.
Uploaded video as a demonstration, but the recording is a bit buggy, my apologies, but you can see the issue there.

STEPS TO REPRODUCE
1. Open and maximize Dolphin (Or any other program)
2. Close the program
3. Reopen the program (It will reopen in the maximized state)
4. Drag it from top to move it into a floating state
5. Try to resize the window using any border/corner except for bottom left (That one works correctly) -> Window jumps to a small size

OBSERVED RESULT
Resizing program opened in a maximized state results in the program window to jump to a small size on its own.

EXPECTED RESULT
Window resized in a direction user wanted.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.0.4
KDE Frameworks Version: 6.1.0
Qt Version: 6.7.0
Kernel Version: 6.8.6-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 4 × Intel® Core™ i5-6600K CPU @ 3.50GHz
Memory: 7.7 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 970/PCIe/SSE2
Nvidia driver: 550.67

ADDITIONAL INFORMATION
Bug is not reproducible when the app is opened in the floating state. It must be maximized at the time of closing it. 

This is an old issue for me. Also happened in 5.x version of Plasma, both on my PC and laptop (Intel+Nvidia using nouveau drivers)