Both Chris and Jim have their boards to work with. Chris has started to work with his and rotors TX is sending packets but not receiving any packets yet. Still working to understand issue.
It could be hardware or software.
To help sort out issues with the AX5043 I have made up a table (attached) to correlate the Select, IRQ lines with the physical chip on the board. All four AX5043s should have an RX signal so in theory any one of them could be used to receive signals. However there could be a hardware issue with any of them. The RX3 AX5043 at the top of board is configured to work single ended. The three other devices are working differentially. The code may need different register settings for each of these to work properly but in terms of the AX5043 I think they all should be looking for a differential signal. I expect the signal strength of RX3 will be lower.
Bob