@davegray 

It does sound like your device is holding its connection to the Inside AX11000 router and not moving to the outdoors 610

This is likely due to the fact the two devices, despite having the same SSID are not capable of roaming between themselves, it will be the client deciding to roam and from experience.. they hold on to the old AP until grim death.

You would be best finding out if that is the case, see if you can see yourself connected to the AX11000 from outside, if so try reducing the power level.. or set the RSSI limit to kick the device off earlier, that way it will reconnect to the 610 AP

  @davegray I think the AX11000 uses OneMesh, and is not compatible with the Mesh on EAP Business Devices, however your comment makes it sound like this setup was working to your satisfaction at one time.  Since the Mesh is not compatible between the two I am not sure how. Regardless since the only thing you did was change out the AX11000, I would think something in the settings is different. Do you have a backup configuration from the original AX11000?  The Seamless Roaming is not going to work but at least you may get it back to the state you originally had it.