This is a generic solution, I did these steps before posting here.
And bluetooth connectivity issue not at all problem, after connecting, audio is not playing, however I could get notification sounds & alert.

It's not happening to one BT Device, I tested with multiple devices, in some devices audio is playing very low volume (if keep device at ear, then only it's audible), while others it's not at all playing anything.

As I said, alerts I can hear