There are two fuses for the Bluetooth system in Each i-bus BMW (including X5)
1) KLR ignition switched power
2) KL30 Power

With either fuse out the system would not even turn on.

There is no fuse for the speakers.

Please describe your issue in detail so that I can narrow down the issue and try to help you out.

1) You mentioned that it worked perfectly before. Is that correct.
2) You mentioned that the ULF charged one phone, but not the other. Is that correct

3) Where you ever able to hear the other party speaking with the system?

4) Press and hold the pairing button and say "Help Phone" Does it say anything? If so then we can narrow down the issue further.

5) Where did you get the 1st generation ULF module? Do they have a return policy?

6) Can you open the cover on the electronics acccess area to reach the wiring? If so, check to see that the connection is solid. It is possible what you describe is related to a loose connection in the eject box.

Martin