Mode Zero

I have recently purchased a JR RS70 rx. It is a 35Mhz synthesized crystal PPM 7 channel rx. I am planning to use it with my Courier tx with modern servos. I haven't tried it with the Courier yet because the battery is flat, charging now. I have tried it with a couple of cheap txs as supplied with twister indoor helicopters. It picks up the tx when it scans for the channel it is on and works fine if you move the sticks slowly as you might when flying. But when you bang the stick over as you would perhaps when doing a quick preflight "is it all working" check the servo stops part way through it's travel. If you keep the hard over stick position and wait a few seconds it catches up. Analogue or digital servo is the same. Use it with a JR388 tx or the MC24 tx it behaves as you would expect with no lag. I have used all these txs with Hitec 5 channel rxs and not had this issue.
Any you clever people out there shed any light on this by way of explanation?

My guess is that the JR Rx computer algorithm scans for JR signals first and then scans for foreign signals to decode. If the signals change rapidly enough, the Rx cannot scan and decode fast enough to keep up. It seems the scan and decode sequence happens every time there is a change in the signal.