MiniVan and the door that sticks

I have dealt with door locks before on houses. I have changed them door by door to have all matching keys or to change them from the previous owner… what I’m not capable of doing is fixing the $&#$ lock on my sliding door on my minivan. It sometimes locks and does not unlock. Unless you manually unlock it from the inside. It’s bad enough that the heat makes the door stick (known problem at the dealer ship who swears every time they ‘fix it’ that it won’t happen again), but to have a door that won’t open and you don’t know if it is stuck or if it is locked. I think I have pulled my shoulder out twice due to this problem. Which I blame on my inability to do pushups… it hurts horribly to do them after I fight with that minivan door!