Some other good points here. Always turn the Tx on before the Rx and always turn the Tx off after the Rx. The receiver looks for any signal and will accept the strongest. (OK - so the new 2.4 GHz get past that to some extent). And any time you're overly close it may cause the Parkinson's glitches you describe. As may low bettery voltage, EMI or a bad antenna or antenna connection. Do a range check (with an assistant or by watching the control sufaces carefully and see if it persists.