We once had a semi-retired Hangar Queen transferred to our unit after it had been cannibalized for spare parts until our supply system caught up with demand.
Our mechanics (Engineers to the not. knowing) put her together again and off we went to do air tests....job done and she was put to work with the other Fifteen assigned aircraft.
Each time she went out....if she went Northwest towards the Cambodian Border and Indian Country....one of the engines would fix at a low power setting and nothing would cure the problem....go anywhere else and she worked fine. (I am not making this up.)
Everything she was returned for maintenance action....with air tests....no fault found was the result.
This went on for a month....and sure as houses...if she went Northwest...back she came.....with different crews each time (we thought it might be a crew issue.....).
One day...one of the mechanics being a brighter spark than most but who was guilty of the greatest Sin in the. military....being an independent thinker...upon reflection and much study of the Maintenance manual started chasing wires...wire bundles...and connectors for the various engine control systems.
One the "good engine" side...he found a pin pushed back on a connector on the a system that had to do with both engines....not just each engine....and just like that....the old girl was able to go to t he Northwest again.
Only the Gremlins know why it was only flying to the Northwest that had to do with the problem....them being the sneaky rascals they are.
They were undone by a Technician that knew what he was doing and would not give up until he found the fault.