I have been experiencing this same issue with all 4 of the Surface Pro 4's that our salesgroup are using.
Its the same issue. They will report random events where they show connected to the WLAN but unable to access websites. At the same time they are unable to ping the gateway or anything beyond. Disconnecting from the SSID and reconnecting will resolve the issue as will uninstalling the adapter in device manager and letting the OS reinstall it.
I have tried using an external USB WLAN adapter but the issue occurs on that as well. The rest of the employees here use Dell latitude laptops all running Intel 7265 adapters with current drivers and not a single report of any issues. We also are using AP-325s with a 7010 controller and currently on 6.5.3.0.
The Surface Pro 4's are using a Marvell Avastar NIC with driver version 15.68.9112.23 from 12/2016 which is the latest version according to MS driver site.
By chance is this happening when the users are docked to the Surface docking station or when they are undocked? All of these issues appear to us when they are docked. I have yet to have an issue reported when they are undocked. Some of the online reports have pointed to the dock as the potential culprit but I have not been able to make that determination definitively.
If you do a search on Surface Pro 4 wireless you will get a bunch of results where users are reporting this exact same issue but no resolution or confirmation of an issue from MS.
I do not believe in any way that this is an Aruba WLAN issue. My feeling is that this is an issue in the way the OS is managing the adapter or something in the Surface docks. Having experienced this issue with both the internal adapter and also with an external USB adapter is perplexing and strange. My next troubleshooting step will be to put the external USB adapter in the dock and turn off the internal Marvell adapter and see if the issue still occurs.