no FF with some TS files

I discovered that in some TS files I cannot use the fast forward function. Likewise, when starting the movie, the “continue” function does not work. In all those cases media player goes back to the library view. The same behaviour with those files occurs in XBMC. The strange thing is that other TS files play well and I do not see any reason for this different behaviour. All TS files (the working ones and the others) are recorded from  the TV by a Synology Disk Station (video station). Any ideas?  

i have the same problem with a mkv-file.