RBK852 unbearably slow

[simultech2]

I have had an Orbi RBK852 for about 3 months in a larger house (ISP router doesn't reaching far enough), and its unbearably slow.  I'm at a loss of what I can try, so looking for any ideas.  Here is the speeds from my tests.  I have Xfinity ISP, all speeds via speedtest.net.

Xfinity Router Ethernet - 900mbps

Xfinity Router Wifi - 600mbps

Orbi Ethernet - 200mbps

Orbi Wifi - 80mbsp

Orbi is plugged directly into Xfinity router, and my xfinity router ethernet test was done with the same cable/port plugged directly into a PC (so its not cable, port or anything on the xfinity side). Tried factory resetting twice, disabling the satellite and ensuring no other devices wired or wireless on the network.  My theory is that its the orbi itself is just broken, given its ~25% of the speed and all wired up. 

Any thoughts or ideas at all?  Any help appreciated, I'm ready to throw it in the bin and buy something else.

(re-posting from https://community.netgear.com/t5/Orbi/RBK852-unbearably-slow/m-p/2164373#M128752 based on recommendation).

[FURRYe38]

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?

If your ISP modem has a built in router and wifi, This would be a double NAT (two router) condition which isn't recommended. https://kb.netgear.com/30186/What-is-Double-NAT
https://kb.netgear.com/30187/How-to-fix-issues-with-Double-NAT
Couple of options,
1. Configure the modem for transparent bridge or modem only mode. Then use the Orbi router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ/ExposedHost or IP Pass-Through for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.
3. Or disable all wifi radios on the modem and connect the Orbi router to the modem, configure AP mode on the Orbi router. https://kb.netgear.com/31218/How-do-I-configure-my-Orbi-router-to-act-as-an-access-point and https://www.youtube.com/watch?v=H7LOcJ8GdDo&app=desktop