Content I play regularly through MC25 includes:
Television (typically 720p or 1080i at 59.94fps)
BluRay MKV (1080p at 23.976fps)
UHD BluRay MKV with HDR (2160p at 23.976fps)
I have discovered that with Options / Video / Display Settings / Display Settings automatic change mode: On, framerates wouldn't change back from 23.976 to broadcast-television standard, causing jerkiness. I fixed that by STOPPING playback (Ctrl+S) instead of merely exiting out of the playback to the Theatre Mode main menu.
However... If I play a UHD BluRay MKV with HDR, then MC25 does successfully trigger HDR on my LG OLED for playback of that media (and it looks spectacular!), but even when I STOP playback, no other non-HDR content will playback properly. All subsequent content triggers the HDR, and looks obviously wrong. This persists even after EXITing MC25. The only cure is a computer RESTART (or SHUTDOWN / Bootup).
Any ideas? Thanks!