wireless Interference affecting multiple WAX610 AP dropping clients

I have 3 WAX610 Wireless AP around my 2 storey house to get effective coverage. I have been having issues with some (usually Apple) devices hunting for connection and  constantly switching between access points despite having a reasonable signal on the AP closest to them. 

I have put each of the access points on separate 2.4GHz channels (1,6 and 11) and there aren't many competing networks close to me on that band and I can see no other 5GHz networks at all (I have used channels 36, 48 ad 161 in 5GHz).

A check of Insight Notifications reveals messages like below:

Despite the messages above my phone did in fact have a wifi signal and IP address.

And the chart of wireless client connections looks like the below

I notice on wifi analyzer that I'm getting a spike pattern simultaneously on all of the AP's and am wondering if this has anything to do with the issues I'm having. Again, the three AP's in my network are on non-overlapping 2.4GHz channels but all experience the spikes at the same time

Does anyone have any thoughts as to why I might be experiencing these constant drops and what could be causing the spikes in signal strength?

Cloud Managed WiFi 6 (WAX610)