LE 13 N stopped smooth playback on 4K on May 11 nightly?

Hello,
Just curious, here the last nightly to play back smooth video is LibreELEC-RPi4.aarch64-13.0-nightly-20260511-f6935c9 which still runs perfectly.
Any version after that has issues with the 4K HDR stuff that we see much of.
Is this a known issue, a breaking change, or something we need to tweak?
Thanks for a great bit of code an any hints if there is time.