Oh, the goddamn container bug. OK, that one was probably even worse than Judy. We finally found the problem while developing Ultima Underworld II. You will thi

Oh, the goddamn container bug. OK, that one was probably even worse than Judy. We finally found the problem while developing Ultima Underworld II. You will think we were complete idiots for not using this process (described below) to find it earlier, but it was 1992, we were straight out of school, and we basically discovered all our debugging techniques ourselves. We knew (even during UW development, I think) that it was possible for your inventory to get corrupted. We even wrote debugging code that would trawl the entire object system ensuring its validity; the problem was that, especially on PCs at the time, running it all the time slowed down the system too much, even just for local testing. Our eventual bright idea (duh) was to run it just once every few seconds, assuming that whatever corrupted the object system was likely to be due, however indirectly, to player input. The hope was that when the assert fired the player would have just done something noticeable, and we could then look into the code that followed from that behavior. Sure enough, a few days later, the assert fired right after a tester threw a bag into the water. And it turned out that's where the bug was.