Bill,
Not sure if your question is directed at me?
In any event I thought i had answered what fixed the issue for me... if not here goes...
So my issue 'WAS' that i could not stay connected to 5GHZ unless i either turned off my sim or restarted my phone. And then it would only last for a few hours before it dropped the 5GHZ and switched to 2GHZ.
What i did was first I ran the windows phone recovery tool and installed the latest public (NOT INSIDER) firmware. (please see my previous post about the numbers as i no longer recall and don't feel like going back) After i did that i rebooted my phone
and then connected up to 5GHZ... It stayed connected all day, i left the area and came back later and it was able to connect back up to 5GHZ. I've since had a few firmware updates/releases installed and I still do NOT have any problems with connecting and
staying connected to 5GHZ.
I do have the dual sim 950xl but it only has a single sim in it currently. I am also in the U.S. and using ATT.
I have several different 5GHZ routers that i connect to throughout the day. (Cisco, Asus, Netgear, and others)
I can't speak to folks outside the U.S. having issues or if you have a 950. The 950 and 950xl are somewhat different hardware wise so what works on one might not work on the other. However the problem seemed to be more to do with the sim interfering with
the 5GHZ band. (shutting off the sim would allow me to stay connected to the wifi networks which at the time i didn't give much thought to) But like i mentioned since doing the update (using the Microsoft phone restore tool) I have not had any problems.
There was some issues the first day with some random reboots but that stopped after the first day.
Should Microsoft have released a phone with these problems? No.. they should have done QA testing.
However if you are running the insider build, well you can't complain about things working because you are beta-testing for free Microsoft's program and they do have a rather lengthy disclaimer that states 'you may have problems.' Anyways, if you need
more information on exact steps PM me. Otherwise that's about all I have to say on the matter.