X60 in access point mode completely unusable
For a few years I have been running a mesh home wireless network using three M9Plus units in Access Point mode. The configuration: Cable modem -->(cable)--> Archer C7 with WiFi disabled, used as router --> (cable) --> Main M9Plus unit -->(wireless) --> 2 M9Plus units. This setup has been reasonably stable (one notable exception: bringing up the network after a power outage is royal pain the the neck) but somewhat slow so I decided to upgrade to X60. I've added X60 to deco app and defined it as a main deco. Unfortunately the network became totally unstable, secondary deco units refused to connect, devices throughout the house started to drop WiFi connection. After a lot of digging I discovered that the moment I switch X60 to wireless router mode it starts the work properly. When I go back to Access point mode the network becomes unstable again. Just to be sure the X60 is the root cause of the problem I removed all secodary decos. Even in this configuration - a single X60 in access point mode connected by cable to my router - it is completely unstable to the point it is unusable.
All devices are on the latest available firmware. 1.5.1
Is my X60 faulty ot this is a known issue? Any solutions/workarounds?