RAX40 crashes when netgear range extender is connected

I replaced my R6300 WiFi router with a new RAX40 WiFi Router (and new NetGear cable modem too) . With my old WiFi router my WN3500RP extender work almost flawlessly in both 2.5 and 5G range extending, needing an occasional unplugging to reconnect. But was having full system speed and disconnect issues so bought all new equipment, unnecessarily, as problem was failing filter at utility pole. Thanks Spectrum! Not.

THE PROBLEM. Every time I try to connect my Range Extender my primary WiFi stops broadcasting from router (NETGEAR88 2.5G & NETGEAR88 5G) drop from available WiFi signal for all wireless devises and (NETGEAR88 2.5G EXT & NETGEAR88 5G EXT) become the only detectable WiFi signals and they show ‘no internet connection’. To make wireless usable again I have to unplug the modem and router to get wireless internet back. Note, sometime my modem internet connection light will also turn yellow at same time primary WiFi drops. Very frustrating. This is the second RAX40 Router it has done this with. First RAX40 ultimately died after multiple crashes, WiFi dropping signal and in the end a reset (using reset button) wouldn’t reset it either. I don’t nderstand how a NETGEAR Range Extender can be having such repeated and singled out confirmation of issue to a top performing and expensive router (and form too).

Any ideas? Really need to use range extender for its Ethernet connection more than anything for home A/V equipment.