My apologies on intruding on this discussion, but since the OP has both a C2 and an Intel-based box, I'd like to ask whether upgrading from 11 to 12 on C2 introduced any issues on H264 playback. Specifically:
* seeking causes artifacting to appear
* in worse cases, kodi restarts
* in general the frequency of problems with H264 increased dramatically on 12 (on 11 I can't recall having any issues at all)
Do you recall encountering any similar issues on H264 material after upgrading to LE12?