I've been there. It takes many hours to try to guess where the system went wrong to produce the undesirable result, and then you still might not be sure if you are looking at the right place, and then there are always environment issues, you aren't sure of. So, you don't know who to blame.
Only very simple systems will reproduce pathological results 100% of the time given some initial conditions. The bane of complex systems is the timeouts. They are usually very hard to justify and are easy to blame for undesirable behavior.