Okay I solved the problem by the other way.
Previously I open the media file every time we need, cause I have several individual media movie files.
But I found the ram usage will get higher and higher when opening files every time.
I think that’s the problem is, once the ram over some computer limit then it’ll freeze.
The solution for me:
Use 1 single full length video, and using SEEK function to jump to the timecode you would like to play.
Like spritesheet save ram for old game. This way can do the same thing.