Cases where I have seen "monthly blows"

Of course, the (in)famous noise caused problems, otherwise

Interrupt at 2 priorities coinciding with maximum stack use (stack blow).

A device producing a (noise) value that the code had not eliminated (array overflow).

A condition involving specific interrupt sequence just before (2 instructions or less, if I recall) a watchdog kick.

A register used in two interrupt routines at different priorities but same register bank.

Serial buffer full not detected and handled (variable at end of buffer overwritten).

I am sure I have seen more, these are what comes to mind, check them and come back.

Erik