Yeah, I am seeing the same issue. i tried installing a newer version of bluez but that did not make a diff.
There is a script that seems like it is intended to enable Bluetooth on the BBs but there is nothing listed for the BBAI.
The script is called bb-wl18xx-bluetooth.
Inside it does a check for the type of board and running manually this shows:
$ cat /proc/device-tree/model | sed “s/ /_/g” | tr -d ‘\000’
BeagleBoard.org_BeagleBone_AI
There is no option for BBAI in the script so it just will disable the BT.
Cheers,
Jon