Update the firmware and then contact Be if the line continues to drop. They will up the SNR which tends to drop the speed slightly but improves the reliability. You can do this yourself in the DGTeam firmware, but both will have the same effect.
The actual modems in the BeBoxes are usually excellent so if is unlikely to be that dropping the connection. The router functions and wireless quality on the otherhand is a bit hit and miss depending on model sent.
When I was using Be I used the BeBox, then a DGTeam firmware on a Netgear 834 and finally the BeBox in Bridge mode as a modem for a Draytek 2820 router. The BeBox was the best connection, but the functionality of the rest improved with the Netgear and again with the Draytek.