I wouldn't expect any real-world differences between releases as nothing on the kernel side has really changed (nobody did any real work on the decoders since 2020). That said, Kodi and ffmpeg versions changed so it's not impossible. Seeking is generally okay on H264 in my testing, but the decoders are all known to be imperfect, and there are some unresolved memory buffer management issues that when provoked with lots of stop/start/seek activity will leave the decoder driver in a bad state, although I've not see any Kodi crash/restarts from them.
The sole real-world decoding change is https://github.com/chewitt/linux/…aa21f07ee54d028
This is baffling to say the least. And apologies again for jumping OT, but I really needed the feedback of the OP in the other thread, since he is in the same boat and might be able to confirm (or not) my own experiences.
It's funny: I honestly can't recall any issues at all on LE11 with H264 playback. Something has definitely changed, but from what you're saying it seems hard to track and, judging from the size of C2 installations, IMO not worth the hussle.
But again, thank you for taking the time to address my issues 
C2 is the most popular AMLGX board. Not huge numbers, but enough that a negative change between releases would show up in forum reports (despite the effort to downplay expectations with AMLGX). If you have media that reliably reproduces a problem with the current LE13 nightlies, I'd appreciate an extract or copy for testing.
