The rear door of my 89 16" Double Cab won't unlock. The latches are the same
as the regular Vanagon front door latches.

Use to work fine until last week. I shut the door. It closed just like
normal. When I tried to unlock it a day later, the lock button won't go all
the way up.

I dismantled the inside panel so that I can reach the latch mechanism from
inside. However, no probing or pushing by hand at the latch itself can
disengage the lock.

Any ideas? I'm trying to avoid cutting the mechanism apart but I just can't
figure what's keeping it from popping up.

Thanks,
BenT