On Wednesday night my Deco X90 suddenly became really unstable and keeps dropping my Grid connect devices, My Place air con app, Ecovacs mop/vacuum and ring cameras.

I acknowledge that one of the fixes may be to move all these types of devices to the IOT network but I am not convinced that will fix it as I haven't had any issues for over 2 years to Wednesday so note sure I would be wasting time moving them all over to the IOT network and still have the issue.

I have even tried swapping the 2 Deco X90s around and connecting the lounge room one to the modem. I thought this worked at first because all clients became visible but over time they have dropped out randomly just like before.

My modem has always been a Dlink DSL-3890 and I got the Deco mesh network because the Dlink only supported a limited number of devices. 
Is it possible that something has happened and the deco mesh has inherited the Dlink limited client numbers?