I have made a lot of tests and it seems the problem is not on Odyssey side. I have used SMTube and ClipGrab to stream or download videos from YouTube. I have even converted (ClipGrab + FFmpeg) video from mp4 to Avi. The AmigaOS is always frozen. Only one time I was able to play 360p mp4 without the problem, one time for 1000 test. Doesn't matter if this is streamed, downloaded, with MPlayer-GUI, MPlayer CLI with different -vo and -ao always the same effect.
I have decided to try mplayer -nosound and it is working! I have tried to change Sound setting from CMI8738 to Unit 0. Freeze. Now is even freeze if I want to go back from Unit 0 to CMI8738.
Has anyone the same problem or could make some test? Or I have just found a bug in AmigaOS 4.1 Pre?