Why is P. Albin/Janis Joplin the composer of everything?

Real new newbie. My library was transmogrified from jriver to Roon and now the attribution “J. Albin/Janis Joplin” as the composer on a large number of works has happened. Often the real composer is listed after a comma , at the end.
I know J. Albin/Janis Joplin is correct on Big Brother and the Holding Company but why elsewhere?
Is there a dummies explanation of metadata anywhere?