Using MESH and non-MESH devices in same network?

Here is an odd behavior

I added an Nighthawk X6 AC2200 Tri-Band WiFi Extender EX7700 Mesh Extender

My new configuration is now one router and three extenders

Nighthawk X6 AC3200 Tri-Band WiFi Router R8000
Nighthawk X6S AC3000 Tri-Band WiFi Extender EX8000
Nighthawk X4S AC3000 Tri-Band WiFi Extender EX7500

Nighthawk X6 AC2200 Tri-Band WiFi Extender EX7700 Mesh Extender

Good news - from a usability perspective everything is working as expected. No more dead spot in our basement. We are very happy with performance.

Odd news - from an Admin perspective something is whacked. I can list the extenders with the mywifi url. I can manage 2 of the 3 extenders (ex8000 and ex7500) from anywhere in the house regardless of which extender I connect to.However I cannot manage (log in as Admin to ex7700) unless the computer logging in as admin is on the ex7700 extender. 

Example ... 

if I am downstairs connected to ex7700 I can log into any of the three extenders as admin via mywifiext. Does not matter if I use Mac, ios or windows to log in

if I am upstairs connected to ex8000 or ex7500 I can see all three extenders listed in mywifiex however when I clicked on ex7700 I timeout waiting for the admin page to load.

So bottom line all is working as expected except I must be connected to the extender ex7700 if I want to do any administration on ex7700

 Any clue what can be causing this? This is not preventing  end-user usability but from an admin perspective it is driving me nuts.

thanks