Hi,
Check if you have installed appropriate codecs on your players (SBBs) and also try to optimize your video files by re-encoding them with same codec to same resolution with same frame and bit rate.
I recommend H.264 BP/MP/HP, 1920x1080, 25 or 30 fps in 25 Mbit.
Regards,
Ivan
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Ivan Sabolovi?, DSCE
Digital Signage Consultant
www.mundusdigitalis.com