Try if blacklisting Gabest MPEG Video Decoder in BS.Player (so that it cannot use it anymore and BS.Player has to search for another available decoder) does the trick.
(rightclick >) Options > Preferences > Filter management > [Blacklist/Whitelist]
P.S.:
When you installed BS.Player, did you allow it to download and internally
* install its preferred codecs/filters?
(*internally meaning for use by BS.Player only, not interfering with your system's codecs)