I had a lot of grief with interference for a while.
My Futaba T6XA system would range test to 110 yds with the engine off and only get 30 yds with the engine running.
The engine and radio system had plenty of separation.
I tried another R127DF reciever and no luck.
I tried a Hitec Supreme and problem solved!
I sent both R127DF recievers to Hobby Services for repair. One was new and the other was almost new.
Both were repaired and now range test well in my gasser.
Hope this helps
John