EX6200 connection issues with the firmware version V1.0.3.68_1.1.104

I can also confirm this issue with a Surface Pro 3, running Windows 10 Build 10586.71, driver version 15.68.9037.59 for the Marvell AVASTAR Wireless-AC Network Controller which just rolled out in the last week or so. I updated my AC1200 to this most recent firmware 1.0.3.68_1.1.104 and still the issue persists.

My unit is configured in FastLane mode to broadcast 5Ghz only to devices and use 2.4Ghz as the backhaul to the router. I've changed the setting under Device Manager -> Properties for Marvell AVASTAR Controller -> Advanced Tab -> Band -> 5Ghz Only and confirmed I can successfully connect to the other 5Ghz network coming off my primary AP. However upon attempting to connect to the AC1200 Extender I only get Limited/No Connectivity. I'm prompted for my password (WPA 2 Personal) and it appears to be connecting, but eventually times out and says No Internet. 

Other devices including my new 5Ghz Chromecast and Moto Droid Turbo 2 can connect to the AC1200 Extender with no issues on 5Ghz. To me, this appears to be a driver compatibility issue with the Surface Pro 3 and AC1200 that has not been fully tested. 

For what it's worth, I was having this same issue on the last version of firmware as well (both for the AC network adapter, and the AC1200 - issue persisted after surface was updated, then after AC1200 was updated).

Any suggestions I could try on my end to resolve? Thanks for your feedback!