Ok, thanks, I can produce a working build by myself now.
I did some further testing: Some h264 and also some hevc video files produce green "garbage" on screen when playback is started. This garbage disappears when the next keyframe is seen.
I have a small sample video file uploaded here: https://filebin.net/6gkcb0hab2ra0cox/test2.mkv and a kodi.log when trying to playback that file.
Also a MPEG2/1080i sample file from https://kodi.wiki/view/Samples plays back incorrectly (too fast at first, then choppy).