- install Opensuse 15.6 inside virtualbox. set memory to 2 GB, core count to 4 (core count probably not so important),  do not enable 3d acceleration (it's freezes desktop but I'm not sure it's kwin fault)
- open dolphin, move window (everything is ok for now)
- open firefox open 5-10 tabs with youtube videos  ()
- move dolphin window 
- enjoy slideshow
- close firefox
- move dolphin window (same slideshow)
- wait 
- move dolphin window (same slideshow)
- once kwin got into slideshow mode there is no turning back

- not sure but this could be reproduced on any distro. 
- KWIN_COMPOSE=N kwin_x11 --replace does not help (I tested X and O2 they does not help either)
OpenGL vendor string:                   Mesa
OpenGL renderer string:                 llvmpipe (LLVM 17.0.6, 256 bits)
OpenGL version string:                  4.5 (Compatibility Profile) Mesa 23.3.4
OpenGL shading language version string: 4.50
Driver:                                 LLVMpipe
GPU class:                              Unknown
OpenGL version:                         4.5
GLSL version:                           4.50
Mesa version:                           23.3.4
X server version:                       1.21.1
Linux kernel version:                   6.4
Requires strict binding:                yes
GLSL shaders:                           yes
Texture NPOT support:                   yes
Virtual Machine:                        no