Im agree that help MS Support has given according to this Fslogix problem, is very bad.
But the 2105 preview version did solve our problem, we havent got accept from customer for upgrade to public version of 2105 yet.
Did also experience this problem on another customer, but a simple upgrade to the public version of 2105 version, did solve the problem. (here we experienced fslogix service go nuts, so the VDA lost connection and sense.
May some of you take a full screenshot of your GPO with Fslogix setting?
From my perspective, I would say MS has fixed the problem with 2105 release.