That's annoying... working intermittently is almost worse than not working at all!

Re. chips, that's pretty much what the RC Groups forum said (link):

The latest Lemon 6channel will have the current SDR (Software Defined Radio) RF board, your older Lemon, Spektrum and Orange will have the legacy CYPRESS CYRF6936 chip which is also used in the Deviation transmitters.
And also:

...the latest Spektrum receivers are also an SDR design and no longer use the CYRF6936 chip. the TI 2650 chip that Spektrum use is not the same as the one used by Lemon...
So it may not just be a Lemon issue.

It's not currently a huge issue for me, just a minor inconvenience, as I have the Dx6e which works with every receiver I have, and a bunch of older receivers that work with the Devo 7e no problem. Just thought it was worth flagging up as the Devo 7e and LemonRx both seem pretty popular and this could catch a few people out.