I had these symptoms:
Door won't open, and then interior handle just doesn't feel like its doing anything. You may notice that the outside handle (which also won't open the door) is slow 'return'. Also the interior lock slider doesn't operate as nicely as the other door.
Opening the door: It is just about possible to remove the door card with the door shut (I did), but there's probably no need.
If you waggle the outside handle a few times, and bang the door a bit, you should be able to open from the outside.
Finding the problem: Its probably spring that's broken, which would help the mechanism to 'return' properly and not get in a jam. You will haveto remove the door cards off both doors to get a your head around which control rods should move/return etc. whenyou operate the handles/locks, and where there should be a spring.
Once you work out where there's a spring on the good door, but not on the bad door, you'll understand what's going on.
Replacing the spring: I haven't got there yet- I'll keep you posted if its tricky!
Hope that helps somebody, Dransfield BRG '92 Eunos
Keywords: Door open spring deadlocked handle locked door card latch won't open can't open