@stephenw10  Thanks for your interest. Apologies for attaching this as txt but the only way I could get it past the spam checks.

"Is it still at that com port?"

Yes it is still at /dev/cuaU0. I've tried all the other /dev/cuaUx ports but only /dev/cuaU0 port successfully obtains valid addressing details.

"You are using the ue0 device to actually connect over I assume?"

No, the interface is configured as a ppp on modem port /dev/cuaU0. (I'm in Australia & to the best of my knowledge none of our mobile broadband providers support connection on a direct ethernet port, but I'll be happy to be corrected on that if there's an alternate connection method available).

"It just doesn't dial out now?"

It obviously dials out ok on fresh boot as the interface has all it's valid IPv4 addressing (interface address, gateway address etc), but it just won't pass any data. Disconnecting the interface via the Status - Interfaces page brings the interface down, but it never successfully reconnects via that method. Only a reboot gets it back to valid addressing details.

Hope that clarifies the situation. I have rolled the production device back to 2.4.5-p1 for now, but do have an identical set of hardware to test/diagnose on.