USG and Comcast/ATT Failover

I have USG (with recent but not the current FW) with Comcast on one wan and ATT on the other, failover is enabled and I’ve seen it function properly when I pull the cables. But it appears that the primary Comcast connection doesn’t recover properly if the failure is somewhere in the comcast network. The cable remains active because the modem remains “running” and the network connection remains linked so maybe USG doesn’t “see” it?

In this condition the Lan clients have no internet access, I also don’t receive any email notification until the device returns to the comcast side and that’s only after a power cycle. I would have thought I would see an email from the switchover to the ATT side. I can’t reach the site remotely during these events either and I am never at the site when this failure occurs so I can’t look at the USG locally for more info. The client power cycles the USG since that works and they are back up.

I’m not a fan of things that require a power cycle to fix, can anyone tell me what is happening here?

Has no one had this experience before? It just happened again yesterday and I was able see it in action. The USG looked fine on the exterior, LEDs were active and the logo was not a trouble color, but the browser interface was unreachable - so a power cycle was ultimately what was required to restore function.