I ran a fresh build of 9.2.7 and noticed no errors in the log, playing back the incriminating file on the Pi4.
I am now running it on my old install, with MANY addons disabled.
Getting this one only as a fault.
2021-07-07 09:48:55.192 T:2433688432 WARNING: CMMALVideo::GetPicture - ret(0) pics(0) inputs(0) slept(500) queued(0.33) (484.44:484.11) full(0) flag>
2021-07-07 09:48:57.851 T:2433688432 WARNING: Previous line repeats 4 times.