[PROBLEM] most movies do not play

[bonestaak]

I have a Raspberry pi2 after installing openelec, osmc, i finally used Xbian.
All my movies / music movies are on a Synology. I used NFS to connect.

Although the screen is more user friendly then openelec. most movies won't start. i have 60 mixed movies as mp4, Img, Vob but only 2 of the 60 movies plays. The screen went black for aboud 5 seconds and then i am back in the main screen.
What should be wrong?