This is a good review / article comparing Anker with other brand, Bose. Something on the BT pairing with the Soundlink mini is very unfortunate, I use it most of the time in my study, and this BT has worked 100% each time. Unless you are using iPhone with a Developer iOS, have not seen any other issues for pairing Bose devices. Cannot say much about Soundcore Flare, as I am yet to own it.
Which phone did you use, and had the issue? Also, have you tried pairing with other phones / tabs / PC and seen this occur? This may help understand what may be happening