If you have the SOS button/BMW assist, bluetooth is controlled by the TCU. USB hubs don't go bad often. They are only used to split the signal for the unused phone cradle in the arm rest. Finding and testing the USB hub is not easy. It would be simpler to just run a new cable between the MULF and console.
https://www.ebay.com/itm/For-BMW-CIC...kAAOSwc2FaJKyR
Did you replace the MULF? If so did you have it coded? It may need to be reset to the options your X5 has. As for the Avin, there are a few threads on those. All of this may be unnecessary if the Avin replaces it.