Opening corrupted DMG?

I have an old time machine backup dmg that used to open up in finder but recently it has said "no mountable file systems" when I try to load it up. It is encrypted and the password works and the file is still the same size it was. Anyway to fix it?

Tried repairing them with disk utility but it is unable to repair. One DMG file says "Invalid B-Tree node size".



Other one is just a "could not be verified completely"