Serviio

Hi,
anyone knows why some files (mostly wmv's) don't FF or REW or Time Search.
I tried with several files and some Time Search work and other don't.
Same codec, same resolution. Same profile (Format Profile in WMV)
So why? Anyone knows?

IS NOT RELATED TO SERVIIO, BECAUSE A CHECK THRU USB AND SAME BEHAVIOUR.

Thanks in advance!