Had this happen a couple of times now in TBP. I get the following:
Int3(): From e:\storage\fso\fs2_open\code\ai\aicode.cpp at line 3306
if (attacker == attacked) {
Int3(); // Bogus! Who tried to get me to attack myself! Trace out and fix!
return;
Don't know if it's a bug or just a fluke that happens now and then. I can play the same mission for days and not get it then all of sudden it pops up out of nowhere. Just played a mission I played several times over the last couple of days and half an hour or so into it (and of course just when I'm about at the end) it pops up.