You need to unecm that, or rather get a new rip. I think I know where you got it and they offer notoriously bad rips of games for Disc based systems.
I made a PS1 Tutorial and Dealt with the BIOS files. The mednafen info file has the names of the BIOS that you need, but the one that you can rename I don't think is Japanese. Regardless, a 1001 BIOS can be renamed to the 5001 BIOS and be just fine, they just all need to match the proper naming. I would venture a guess that the rip is potentially bad on all of them, especially anything you get that is ecm'ed.