Anyone dealt with fax issues on AT&T IP Flex with an EdgeMarc managed router?

Last night I switched from an old (slower) IP Flex circuit to a new (faster) one. As part of the change the managed router went from a Cisco 2900 series to an EdgeMarc 4808. I'm now having faxing issue, primarily with reviving inbound faxes but outbound is less reliable (more attempts needed to connect). Prior to this change, I had 6 years combined of pretty much no issues on the old circuit and the circuit prior to that (both used same managed Cisco 2900 router)

Physical connection wise, it's a somewhat unusual setup with a PRI conversion in the middle: AT&T Fiber into EdgeMarc 4808. PRI handoff out of 4808 to PRI interface on my Cisco 2851, and then GigE out of 2851 into the voice VLAN where the phone system sits (it's the fax server as well).

I'm using g711ulaw on my end, ATT takes whatever I negotiate with, but they default to g729 first. Fax relay is enabled on my 2851 with fallback as pass-through g711ulaw. Engineer said my inbound test faxes start as g729 the re-invite to g711. He also said he's seeing it switch to T.38 on his router, but I never see that on my router for an inbound fax. When I outbound fax, I see g711ulaw and then switch to T.38 14400

What I am seeing on the surface is an inbound fax attempts comes in and it's picked up by the phone system, codec is g711ulaw. Your usual fax noises start from the fax server subsystem of the phone system and when I record the call, I hear them, but the call just stays like that. Eventually the sending fax machine quits and goes into retry. It seems like the sending machine isn't hearing tones properly and starting to send.

I have my VAR involved who provided support on the phone system (Genesys PureConnect, formerly Interactive Intelligence CIC) to help nail down in the logs what's going on.

Wondering if anyone has dealt with something like this where it's possible there is something specific to EdgeMarc routers that needs to be done different vs. the Cisco router AT&T used on the old circuits. Looking for things to throw back at AT&T when I get back on with the engineer. I've also asked for an escalation to get additional eyes on it from their end.