Mine didn't even last two days after the factory reset and restore, so I've done another reset without the restore. Running out of options now.
Now for the good news, I think.
Today I phoned BT tech support. They have far more control of our discs and hub than is available to us. The techie was very helpful. She found an instruction in the disc setup to prevent the backhaul channel from switching to 2.4Ghz, ie backhaul will now only operate on 5Ghz. Discs still connect devices at either 2.4 or 5Ghz.
Time will tell, but I am quietly optimistic.
Sadly that didn't take long. One of my discs dropped the 5Ghz signal and needed resetting.
Completely different SH2 and Disc. It lasted 5 days before dropping to 2.4 GHz. Still no recognition that this bug exists and a fix is being worked upon. A remote disc reboot would help!
After the disc has dropped to 2.4 GHz, if you reboot the SH2 via the SH2 Manager the disc does not reconnect!