Mine seems to have a mind of its own as well. I have tried changing settings like you and nothing helps. Doesn't matter what access point I am on either, still does it. Just glad I am not the only one and hope that an update happens to address it.
It's all very strange. At work, set to auto it never does the connect / disconnect thing.
At home on 5Ghz it was fine. On 2.4 it was fine. On auto it was constantly connecting and disconnecting.
Sunday I bought one of the new Netgear high end AC band wireless routers. It now works perfectly on auto and when set to 5Ghz I get 24 MBPS in my basement with the router in my second floor office In the kitchen on the first floor it is getting just a hair under 35 and it is rock solid.