What Fault Codes Wasted the Most of Your Time - Where the Code Lied?

Curious what other techs have run into. I've had plenty of situations where a drive or PLC fault code pointed one direction and the actual problem was somewhere else entirely. I've chased ground faults that turned out to be a bad connection somewhere else. Overload trips that were actually a mechanical bind.

What fault codes burned you? What actually turned out to be wrong, and how long did it take to figure it out? If you don't mind posting how you ended up fixing it, that would be great too. Might help someone else someday.