Motorola RAZR V3xx

Hello! I have an '08 Jeep with "U-connect" handsfree unit. It has worked well with my older V3 and other V3xx phones. However, after inserting my current phone into the laundry, I picked up a couple of used V3xx from E-bay. One works ok and the other connects, then disconnects, then connects, and on and on. I've tried doing the boot command, and still no go. I've tried using different "priorities" on the U-connect, still no go--one phone works Ok the other, not so!

Any ideas? Thnx, Jack