Cisco Wireless :: 5508 Handheld Scanners Not Finding Wi-Fi Network

Three weeks ago I moved all the APs at one of our sites from WISMs (running 5.2.193) over to a pair of 5508s (running 7.0.220) and everything appeared to be fine through testing and implementation.  We've got about 400 devices on this network and almost everything is working without issue, except for about 10 Honeywell Dolphin hand-held scanners that our distribution department uses.  On occasion when the users go to use them, even when sitting 15 feet from an AP, the device will kick out an error that the "wireless network was not found - please move closer to an access point or return to cradle".
 
As much as I would love to say it's a device issue, they said the problem started the same day I moved the APs to the new controllers (they gave me the date they started experiencing the issue, I was able to link that back to the date I made the move).  They worked without issue on the old controllers / code and, for the most part, both old and new controllers are configured similarly (except for enabling a few new feature that the new code supports like client-link and band-select).  These are b/g clients and I did diable all .11b data rates when moving to the new controller.  Also, this happens in multiple locations, not just in the receiving / distribution area.
 
Lastly, I'm at my wit's end on this.  The issue is totally random and when they are having an issue I can't even see the device trying to connect (by debugging the client on the controller).  One suggestion I've made is that we may need to upgrade the device firmware, but I'm not sure why it would work with the old controllers and not the new.  I guess the worst case scenario is that I can move the couple APs they have in the receiving area back to the old controllers to see if the issue continues.