I remember learning A* at uni while at the same time experiencing it's quirks on our shared minecraft server.

The server was really chugging and so I ran a trace on it. I found the zombies were stuck in a loop trying to find their way into a village that we had completely secured with a large fence. Being a naive implementation (at the time) it meant they never gave up.

I recall there being a bug report with a good amount of detail about how they were going about fixing it.