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 900Mbps/50Mbps)>CAX80(Modem Mode)>RBK853 v126.96.36.199(Router Mode)
Additional NG HW: C7800/CM1100/CM1200/CM2000, Orbi CBK40, RBK853, R7800, R7960P, EX7500/EX7700, XR450 and WNHDE111