Change extension to *.musx & try playing the file in a player with VGMstream plugin. If it remains unplayable then you can request a VGMstream coder to add this version of *.musx format in the next update. BTW what is the size of __common__streamdata.sfx? I'm afraid it's rather big (let's say 40 or 45 MBs) which means it's an SFX bank; my point is it wouldn't make it a high-priority item to add to VGMstream if it's indeed the case with this specific file.