Yeah, actually did a hard reset each time I upgraded the last 2 builds, both seem to be pretty persistent on my 822 & 928 since the 15063 build.
Then again at no point does MS claim to support a Lumia 822 & 928 (spoofed as a 550) so I can't complain too much
Have faith that it will work eventually (and it is not just our older models). After a WDRT cycle to deal with the same BT issue, my L1020 went all the way to build 15215 (by impersonating a 950). The BT issue was resolved along the way (meaning the several "Fast" builds).
I then renamed it back to L1020, largely to recover Lumia Camera. What I do not remember is if the BT resolution happened right after arriving at build 15215 or after renaming back to L1020. I think it was probably by reaching 15215. Once there I was seeing it link readily to the car; and perhaps also by "insisting" with a few soft resets for it to see the other devices. [Darn, I tried so many things!] (BTW, the BT issues had begun to be addressed by MS in this build, if you read between the lines). After this, no more BT issues with the devices that matter most to me, though a few old headsets don't get seen.
Also note:
1. It was immensely surprising that I
did NEVER recover BT by simply going back to Win 8.1 (WDRT) nor during the earlier W10 builds.
Whatever happened, affected something that prevailed despite even a WDRT!!!
2. Not that I really
know this for a fact but if you did
a hardware reset while in the earlier builds, this may have triggered the issue, according to someone. (So, I have avoided the hard resets which I will inevitably have to do one of these days, I suppose.)
3. The BT issues are not happening just to "unqualified models" like ours. Qualified models have had it also.
Lastly, MS seems to mention that more BT tweaking was made in 15222 so, who knows!
Good luck! I am recovering my nerves from the "excitement" during the 15210 & 15215 fast build...then I'll allow the "recklessness gene" to see about 15222