As your service/char fff0/fff4 seems to have several different Notifies cycling through, I would try resetting your BM2 completely, then trying again with a total fresh BM2 without pairing/connecting to the phone and app first.
It works fine with the actual BM2 app. Does not seem to be misbehavior of the BM2.
I can disconnect and reconnect the BM2 if you think it will help, but I dont understand the logic here… I have already disconnected and reconnected it several times while trying to get it working (I swapped it back and forth between a vehicle that often leaves the house and one that stays home all day).