Yeah the linkage mechanism can jam up because of dust etc. The rear barn door isn't sealed that well particularly if the internal plastic liner has been removed.
This happened to me on a camping trip and we had to half empty all our stuff through the back doors to expose the plastic trim on the rear door.
Removed that and sprayed the crap out of it with lubricant (WD40) no probs since (about 3yrs ago now).


I just luv my "clacker Jabber".................