Pay attention to the type of resistance.
E.g:Even if you turn the knob, the latch will not retract.
The knob does not turn to retract the latched latch.
The door lock does not extend until the knob is turned.
More force is needed to turn the knob and unlock the latch.
The handle or knob must be shaken to release the latch.
After the door is opened, try to activate the door lock with the handle. (The simulation opens the door without the latches sticking in and retracting from the striker).
If the door is not open:
After the latch is jammed, you may need to tape the latch enough to retract it to open the door.