SUMMARY
Under KDE Plasma 6.3.5 with Wayland on Manjaro Linux, the system experiences temporary but complete graphical freezes (around 15 seconds) when launching or resuming video playback with multiple OpenGL-accelerated applications. This includes:

    Playing or resuming a video with VLC

    Starting or pausing a video in mpv

    Launching Unreal Tournament 2004 (Linux native)

During the freeze:

    The video sound continues normally (if playing)

    The screen freezes completely (cursor doesn't move)

    After ~15 seconds, everything unfreezes and functions normally

A restart makes it go away, but it reappears after a while. So it's not really happening reliably, BUT when it begins happening, it will happen every time.

STEPS TO REPRODUCE

Log into a Wayland session under KDE Plasma.

Launch VLC or mpv.

Open any video file.

Start, pause, and resume playback.

Observe a full freeze of the graphical session. 

Alternatively:

    Launch UT2004 (Linux native build)

    The system freezes immediately after the graphical context is initialized


OBSERVED RESULT

Computer freeze, with audio still playing in the background.

EXPECTED RESULT
Video playback starts or resumes smoothly with no freeze or graphical interruption.

SOFTWARE/OS VERSIONS
CPU: AMD Ryzen 7 5800X (8 cores, 16 threads)
GPU: AMD Radeon (RADV driver, Mesa)
RAM: 32 GB
Kernel: 6.14.6-2-MANJARO
Mesa: 25.0.5-arch1.1
Plasma: 6.3.5
KWin: 6.3.5
KDE Frameworks: 5.116.0
Qt: 5.15.16
OpenGL version string: 4.6 (Compatibility Profile) Mesa 25.0.5
Shell: Zsh
Session: Wayland


ADDITIONAL INFORMATION

Relevant journalctl logs (trimmed):

[vo/opengl-cb] mpv_render_context_render() not being called or stuck.
kwin_wayland_drm: The main thread was hanging temporarily!


I tried all I could to be able to capture the relevant logs outputs for kwin_wayland with the debug symbols, that you require, but it proved to be beyond my means. Feel free to ask me for further information!