RBR750 - iOS devices fail to get IP address from Orbi + frequent disconnects

For the past  6 months or so, my Orbi RBR750 router & 2 satellites are struggling to keep iPhone & other mobile devices connected to the router. Wifi will drop serveral times during the day. Sometimes the devices will connect with the Orbi Wifi but fail to get any IP addressfrom Orbi's DHCP. Turning wifi on/off a few times on the phone fixes it and IP addresses are assigned (subet 192.168.1.xx). I have "Private Address" on iPhones turned off to allow them to have consistent MAC address presented to Orbi's DHCP service to keep it simple.

Orbi & its 2 satellites are in V4.6.5.14_2.0.54 latest firmware. Firmware upgrades hasve not made a difference in the past 6 months or so though. There are about 30 devices connected to this Orbi. Orbi satellires are 30 ft from each other, the setup was fine in 2020. I have run a Wifi Analyzer to check for inteference from nearby Wifi routers and have tried to set the contentious 2.4Ghz channel to 11 where there are 0 other neighbors. Wifi signal is strong everywhere, when connected Orbi reaches > 700 Mbps. But the Wifi connection is highly unstable. 1 of the 2 satellite is wired for a backhaul with the Orbi router. 

Resetting, rebooting Orbi or iOS network settings etc does not address the above issues. Any suggestions will be much appreciated.