Fast forward issues with WD TV

I have two issues related to Fast forwarding through WD TV media player

  1. In some .MP4 movies,after a particular time,movie gets automatically fast forwarded & not able to stop by pressing any button on remote.I checked same movie on PC,its perfectly well.This issue has happened several times.

  2. In some movies,i am not able to fast forward it.

Can anybody provide soution?