You may want to pull the crystal on both the RX and TX then immediately re-install the respective crystals.

I and others have found that the crystal "feet" get a bit of a patina on the metal that prevents good contact and causes the RX or TX to momentarily stop transmitting or receiving or produce less than good results.

That said, I have a lot of these EDF's from Nitro now, so I purchased a Polk Trakker III TX to handle ALL of them ( 99 model memories! Shift selectable TX with Expo and computer controlled mixes for $140.00 ).