I've got the exact same problem with a P68SC I bought recently. The rest of the gun came in great condition, but the bolt is absoultely stuck in the back.
I've tried doing the soaking method, but the bolt won't budge at all. Being my first sheridan, I'm not overly sure what to look for to sort it out (I've taken plenty of other pistols apart mind, so I've got a basic idea).
I'd appreciate any advice you guys could give on the matter!