Ditto
My rs1compatibilitydlc.psarc file recently started causing issues. Verifying through Steam didn't work for me so I booted up CFSM and started getting the same issue as pictured above. It previously worked for years without issue but now I can't access the songs and any attempts at using CFSM to figure things out are just met with this error.
Maybe check if you have any similar issues with the RS1 dlc pack, if you have it installed at all. It might be something weird there.
Thankfully there are plenty of CDLC alternatives so I'm not too bothered, but I hope there's a fix out there
