Hi Alan,
Your receiver aerial goes inside the fuselage ?? In this case, that's your problem!
If not, but the aerial is alonside the fuselage, same !
Try again, but let leave the aerial free, in the wind.
Had this issue with my P51 (aluminium, aerial taped on one side), fly nice, areial on your side, and glitches aerial the other side (fuselage between me and the aerial...).
Might solve the problem.