RBR10 strange random disconnect of wifi clients

OK I have an interesting case with weird problems.

We have Netgear Orbi RBR10/RBS10 with 2 satellites. The main unit in the center floor, and the satellites in the first and 3rd. It is a single-family house with, standard building construction. We don't have any houses/neighbors within 500 ft and home devices can't pick up any other Wi-Fi signal except our own.

The RBR/RBS are working only as AP - Ubiquity EdgeRouter is working as a router that has an uplink to a fixed wireless antenna/modem.

The mesh devices are like 4 years old. Everything was working fine for >2 years in this house.

The problem developed in the last 2 months - devices started losing connectivity - most of them. You can be in the middle of a Teams call or watching YouTube and bam - no connectivity. You select the wifi network, click connect, and getting the message - can't connect to this network. Forgetting/reconnecting the network or rebooting of the device does not help.

There are only two ways to make the device that lost connectivity to connect to the network again. The first is to reboot/power cycle/onplug/replug the main unit.

Second - without rebooting the main unit, bring the device that lost connectivity very close - a couple of inches within the main unit, then turn on airplane mode and then come back to normal mode. After this, it connects and you can move it around until the situation repeats.

Losing connectivity is completely random both with devices and frequency - there is no pattern like heavy usage, number of devices, etc. It can happen 3 times per day for a given device and go days without it. Also can happen with one device while others continue working.

There are devices that never lost connectivity (or probably we never notice it) - two Rokus attached to TVs. All others - notebooks (all), Apple watches, phones - both Apple/Android experience it to various degrees.

Nothing has changed in the network/setup - nobody was even logging on to the router for years. The main unit was not moved - it is sitting where it was sitting for 2 years. No new devices have been added. Now firmware upgrade/downgrade - BTW, tried downgrading firmware. Did not help.

It is clear that the problem is with the main unit because reboot clears the problem.

 When I mentioned the problem in one group chat someone mentioned that he had seen exactly the same problem several years ago and the only way to fix it was to replace the whole setup.

Anyone have seen something similar? What causes this and what is the right way to fix it?

Thanks