Devo10 -- NRF24L01 stopped transmitting

Got an odd one here that I can't figure out. Hoping to get some guidance on where to stick my probes next.

Been running with my Devo10 happily for some months on the same firmware with no upgrades. All of a sudden, the NRF24L01 seemed to stop transmitting. The radio detects the module at boot (at least it doesn't complain that it can't find it) but my aircraft receiver doesn't get anything.

I opened it up and noticed that squeezing or moving the wires around between the Devo and my NRF could get it to work but only occasionally. I bought a new NRF24L01 radio and re-wired the whole thing up with fresh wires. I've still got the same symptoms. The pads I've soldered to all look intact on the PCB. The voltage at the radio looks good. Chip select is low. I don't have a scope to inspect the SPI traffic, unfortunately. I'm using rechargeable AA's which I charge using the Devo -- the UI reads 10.44 volts.

Any ideas on where you'd start looking next? The wiggling of the wires causing intermittent functionality is puzzling, because all the connections look good and continuity tests agree...

Thanks
Sean

Bump - has anyone seen any similar electrical problems when adding a single module? It seems like using the internal radio (DSMX protocol) is working just fine. I've tried three different NRF24 modules and none of them transmit. The devo doesn't complain about a missing module at hoot so I think at least reading registers is working..

I suppose I could try a 4 in 1 module too but I don't have one.

I poked and prodded until I stumbled on the fix: The CE (chip enable, datasheet says its used to switch between Rx and Tx modes) line on the NRF24 module was left floating. Shorting it to either gnd or Vdd remedies the problem. I don't know which is which but I'm guessing this strap is just overridden in software at init, but if it's left floating the module gets toggled back to Rx mode instead of Tx mode.

But, I don't have a solid reason why this was the root cause. Does anyone know the proper connection for the CE pin on the NRF24L01? Also, the module was working great like this (CE unconnected) for several months so I'm curious to know what would have happened all of a sudden to expose this problem.

Thanks
Sean