3CX Server confused about Phone's Outbound Proxy when two RPi SBC's in one Office?

[uptime1]

There are two RPi SBC's in one office.
One RPi is connected with hardwire LAN Ethernet (10.x.x.x) to a cable modem.
The other RPI connects wirelessly to the same cable modem WiFi (192.168.78.xx)
Both RPI's have the same public IP address since they share the same Internet.
One phone is connected to each SBC.
Everything has been working fine for years.

Sunday early am PST, one of the phones lost registration. After hours of investigation, it appears the unregistered phone (on the hardwire LAN) is being provisioned with an Outbound Proxy IP address on the WiFi network, not it's LAN 10.x.x.x network.

And, shouldn't that Outbound Proxy IP address be the RPI's IP address, as in 10.x.x.x.:5060?

Oddly, if the phones are swapped, they both work successfully. And, if the working WiFi connected RPI and used in place of the wired RPi, the phones work successfully.

No changes have been made to the 3CX server for months.

Thoughts?

 

[JohnS_3CX]

Even if it worked fine for a long time, please do not trust this as a reliable method of SBC deployment.
We do not test phones or SBCs working over WiFi and cannot guarantee they will work reliably and as intended.

Please try to switched to wired LAN if you can and disable the WiFi adapter if possible.