Arris SB8200 LAG (link aggregation) Performance Issues

I recently upgraded my Xfinity plan to Gig service and purchased an Orbi mesh router/network.  I was already using a customer-owned Arris SB8200 modem.  The net setup works great and I can easily get 900+ Mpbs when I do a speed test via the Orbi   I know both the Orbi and the SB8200 can support speeds higher than 1 Gbps but the physical ethernet connection between them would be limited to that  (or slightly slower).   I also know that Xfinity usually provides slightly faster rates than your plan...if supported by your hardware.  As they both supported it, I decided to enable LAG (Link Aggregation) to overcome the 1 Gbps ethernet limit and take full advantage of the 1 Gbps Xfinity plan.  A speed test with LAG enabled showed 1011 Mpbs!  However, then the next morning when I work up, I noticed significant issues with my internet speed and a speed test showed it was less than  5 Mpbs!   I rebooted the  SB8200 and the problem went away.  However, the next morning the same thing happened.   This time I just disconnected the second ethernet cable between the Orbi and  SB8200 and immediately the speed went to normal.  I've disabled LAG and haven't had any issues since, but clearly something is happening overnight that impacts the SB8200 performance when LAG is enabled and requires a reboot/disabling of LAG to correct.

I found a post on here saying that it was a known issue between the SB8200 and Xfinity and a firmware update was needed.  I reached out to Arris and they indicated the Xfinity would be responsible for the firmware.  Any help would be greatly appreciated as I'd love to have LAG turned on and take full advantage of my plan and my hardware.