Had one Pantera in that did this. There are a couple of pieces in the latch/lock that are plastic or die-cast pot metal and can crack, but it wasn't that. Turned out to be loose staking of one part of the lock mechanism. This is NOT the outside pull handle & cup, by the way. A tiny hole drilled thru the staked part and a 4-40 gr-8 screw & self-lock nut fixed the practically unobtainable latch mechanism.
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