We have quite a few of those scanners and quite a few iAP (105 mostly) and have seen the same thing. I'll second the motion to move to A. It's not about the band precisely, it's the signal strength:
The Motorola makes a poor roaming decision when it can still "hear" the distant AP.
Changing bands or considerably limiting max power levels both work, but the reduced max will negatively affect any other devices - especially those with lower power radios.