I spent a lot of time searching various forums and logged all those.
I did run with GB for a while but found 5GHz range was reduced, significantly, and I only live in a flat. The beamforming option on my AC68U was also problematic. So I factory reset and haven't touched since, and I get good 5GHz across my flat - so I can ignore 2.4, which is great, as 2.4 is unusable at weekend. Too many kids with ancient nintendo devices nearby :-/