82 Vanagon sliding door won't open properly

Hello VW lovers! My vanagon's sliding door recently stopped opening properly. From the inside, I have to give it a major hip-check on the rear of the door to get it open. The main latch by the handle pops, but something is stuck at the rear latch. From the outside I can't get it open at all because of the necessary hip-check.

Any ideas here? I don't have the Bently and can't really afford it right now. I have tied to do online research but have not really found anything out. Any help would be soooo appreciated.

Thanks!
Kazza