I`m on June 2016 firmware and I get similiar wifi problems so rolling back would be fine if we all knew what to rollback to but we cant rollback and we cant force an update !
Same issue for me, update in October wrecked my network, I have a similar thread running on here too. BT sent me a new HH6 which I installed yesterday, of course it's running the old firmware SG4B100021EC so all good, I'd like to know if it's possible to prevent it updating again??
I went back to my HH5 while waiting for the new unit to arrive which works perfect, so I will go back full time if this fails again.