UFC Undisputed 3 not booting on Multiman Rebug 4.21

Hi.

I recently installed Rebug 4.21 with its own version of Multiman and when I try to boot UFC Undisputed 3 from my external HDD, ik freezes while "checking files". The eboot and ParamSFO are untouched so I don't know why it doesn't work...

Does someone know?