FWIW, disabling U-APSD on my 7260 (in a ThinkPad T520) totally resolved my issue where I could not reconnect after resuming from sleep. I changed the setting right after I saw this thread about 2 weeks ago, and it reconnects virtually every single time - it might happen once a week, where it happened every time (a dozen times a day) before. I also seem to have consistent throughput now, and the 5Ghz networks no longer mysteriously disappear. (I waited a couple of weeks to make sure I wasn't imagining things.)
My notebook demonstrated these symptoms both at home (Asus RT-AC66U) and at work (Cisco infrastructure, various models) - and *poof* - all is well once I disabled U-APSD.
I've had this adapter for a little over a year now and followed a lot of threads on this forum, but didn't have any major issues until about 2 or 3 months ago. Perhaps that coincides with the first driver containing U-APSD being installed on my notebook? I realize it was a later addition, or at least the setting/option appearing in the driver was.
Thanks!!