Can I verify - are you not on firmware version 4.7.5.1.83.8.204.1.11
Yes I am.... though it isn't the latest and certainly has wifi issues (for me)
This is the latest version supported by BT at current, some users are kind of selected, I guess like a trial for newer firmware but alas most of us are not. So we have the same firmware.
I have firmware version 4.7.5.1.83.8.204.1.11 and it is flawless for me. This is the one most users have.
If you are having issues on this firmware version including SSIDs disappearing as you describe, you almost certainly have a faulty hub. No firmware gonna fix that.
Latest supported firmwares are always published here.
http://bt.custhelp.com/app/answers/detail/a_id/13073...
If somebody has a newer version, they're just part of a sample who are kind of trailing the new firmware. Often this causes them more issues.
Back to the drawing board, your issues do not appear to be the firmware, else I'm sure me and batboy would be raging hell on here, as we are both on the same firmware as you

.
If my SSID randomly disappeared I would be all over that. & If my 5Ghz dropped, again I would be all over that, as all I am using personally is 5Ghz, although other people I live with use 2.4 as well.
I've kicked through 300Gb in a week on this HH5A all over WiFi in the past 6 days.
I may have a spare HomeHub 5A somewhere in my house if you're having this much of an issue getting a replacement out of BT.
Edited by ukhardy07 (Mon 11-Apr-16 23:34:26)