ORIGINAL: ModellbauUK
Just a thought. On my pumps the plastic shielding holds the pump to the motor. Worth checking that air isn't getting in there. Trying jiggling the pump when running the turbine as this may mimic movement in flight.
Will do. Possible I suppose that the movement in flight could be disturbing something like the pump. I'll test with some jiggling and see if any adverse affect on running. Thanks for the suggestion.