What is the Mfr and model# of the ISP modem the NG router is connected too?
If you updated FW, do a full reset on the Orbi router and set it up from scratch, don't configure QoS, Traffic meter or Access Controls. Just do a quick speed test with a ethernet wired PC connected to the router.
My Setup (Cable 200Mb/10Mb)>C7800(Modem Mode)>XR450 w/2xEX7700s
Additional NG HW: CM1100/1200, Orbi CBK40(Gateway Mode), R7800, R7960P, EX7500/EX7700, XR450 and WNHDE111