About the upgrade suspect:
Apparently, the switch from DSL copper to VDSL over fiber is at bottom. The new RG (Pace 5031NV) does not allow adjustment to either SIP ALG or QoS (it's implemented in the hardware), so no tweaks allowed.
BTW: I never said it was OBi202's fault.... it worked for several years, so it is a good product. I did have a OBi100 that failed right after the warranty ran out, but my 110 still runs as well as my 202. I did think that possibly a firmware upgrade may be at fault, but my device was set to manually upgrade, and it was out of date, so I updated it but that didn't change anything. Exhaustive attempts to tweak the configuration settings were made to no avail.
Since my Brother multipurpose Copier/Printer/Fax (8660DN) does not allow lowering the baud rate below 9600bps, I am stuck with this as the slowest I can go. According to Brother, this is the rate to use for Voip. Two other settings to help were tried: Overseas mode and Standard Resolution, but no help. I have another, newer, MFC-9840CDW that I tried and got the same disconnect, so not only is it not the 8660 fax, but the newer 9840 fax is subject to the same issue.
No changes have been made to my ITSP (Anveo), so it is hard to imagine it being the source of the issue. Since it, too, worked previously, I don't think the time to swap ITSPs to be worth it.
At this point, everything points to the PACE 5031NV, and VDSL. The switch from copper to fiber seems to be consistent with other reports on the internet with this same issue of dropped connection on the fax receiving end. I have no option to make further adjustments to compensate for this issue.