For a last ditch solution to the problem, try several different brands or series of XLR connectors. There are subtle differences between Switchcraft, Neutrik X, and Neutrik XX series, for instance. You might find one that still latches adequately. Neutrik also makes a female connector that has a locking ring to prevent it from being unlatched (NC3FX-SPEC), although that counts on the latch still working.
Sennheiser 421s always seemed fussy about this, and my E-V RE-20s never seem to latch fully with X-series connectors (although they're never hand held, so it's not much of a problem).
GTD