I can't say exactly why it happens for u since too little info provided (does those intro video stays [I meant check if it not deletes and with same name] after compression and plays in video player, does intro played fine for u before compression, did u use mass/bulk compressor or single, can u make screenshot of RPGM MV/MZ compression settings, can u upload those 2 compressed intros, did u changed/updated manually ffmpeg UAGC files [ffmpeg.exe in Sripts folder]) coz I've checked both games and all was fine, videos intro played after those both games compression and I say more that for 1st game UAGC wouldn't even probably touched video because it starts compressing for me only with manual non-latin fix. Also nobody complained about such issue long time ago so maybe problem at ur side so try temporary disable AV for testing.