I finally figured this out without even swapping parts. Even though my e39 and E53 both have Bluetooth, they respond in different ways when they reach the phone book limit. My E39 simply says Phone Book empty while the E53 attempts to connect and when it cannot transfer the phone book, it drops the connection and reconnects again. By trimming down my contacts in the phone, the phone connects every time. Another option was to only sync the favorites and not the entire phone book. Odd given that the BT ULF in the E39 is older then the E53.

__________________
2011 550xi Carbon Black/Oyster, M-Sport, Premium Package, Technology Package, Electronic Damper Control, Dynamic Drive, Comfort Access, Active Seats, Surround Cameras

2013 X5 5.0 Space Grey/Black, M-Sport, Premium Package, Technology Package, Comfort Access, Surround Cameras