mkv video problem.. on Vfx software

Hi!
Problem is that on .mkv video on the first play shows well, but if i rewind it back or put it on pause, after pushing play video just shakes and jumps like satellite tv picture on windy day, meanwhile audio plays well... it keeps jumping about 40 sek, then it's back to normal... but problem repeats as soon i use pause or cue or...
no problems with other formats i use : mpeg2, mp4..
liked to use mkv instead of mp4 on SD formats...
using latest beta,
Thanks,
Aivar
Problem is that on .mkv video on the first play shows well, but if i rewind it back or put it on pause, after pushing play video just shakes and jumps like satellite tv picture on windy day, meanwhile audio plays well... it keeps jumping about 40 sek, then it's back to normal... but problem repeats as soon i use pause or cue or...
no problems with other formats i use : mpeg2, mp4..
liked to use mkv instead of mp4 on SD formats...
using latest beta,
Thanks,
Aivar