Vibration test failure
If the module isn't mounted flush with the board and can actually moved by hand it can surely be a reason for a vibration failure. Copper is horrible when repeatedly flexed.
I'd suggest to strain relief the assembly with some elastic compound to the board, if possible (silicone, silastil, whatever is called around you). It's also important to evaluate if the module is 'top heavy', since the regulator body will leverage to the board.