I'm sure this is a stupid question ,but have you oiled itIJIJ Mine gets hard to open ever so often and I just spray some chain lube in the latch and on the bolt and it always frees up. Illinois Gleaner
These latches are very similiar in many applications. If door is latching shut with alot of pressure on latch holding it shut it will unlatch hard. If there is no provision or not enough adjustment to move latch pin outward I would die grind enough material to move it out a bit. Main reason I have seen them style latches open hard is two latch pieces bind on raised area at end of latch pin. Just adding a washer to position pin forward in that application may well free it up. I do believe there is a provision on hinge assembly to slide door for or aft but that is after removing a bunch of screws to get at it. Good luck.