RC Ken is totally correct. A seemingly minor crack in the receiver circuit board, which would be very difficult to see with the eye, could cause intermittent problems (what you are seeing could very well be intermittent problems) as the contacts on the board make/break connections. Don't risk it. Receivers are relatively inexpensive.

I crashed my CG Skylark a while ago, but it was one of those slow-motion crashes, not hard driven into the ground. Nevertheless, the fuselage was damaged forward of the wing and the wing was broken in half at the center point. Everything seemed to work (electroincally) right after the crash, and I knew the problem with the crash was not radio related, but my thick thumbs in landing in a strong wind with minimal throttle.

Later on, I tested the receiver and it seemed ok, but there was something I could not readily identify, a latency in the function of the aileron servo's. They seemed 'delay'ed for some reason. I sent the receiver back and they found a loose component that was probably jarred loose by the crash. It cost me about $20.00 US to get it fixed (plus UPS charges which were minimal). A new receiver cost $49.00 US. The model I put it in cost me right around $200.00 US and still flys after a year and many many take-off's and landings.

Don't risk it. Get it checked and fixed or replace it.

DS.