Credit card issues!

[carwashsystemsinc]

Hi, we operate several self service locations , some with drive through bays. the credit card systems is DRB/Unitec Wash Pay. One of our locations has a very high card rejection rate as compared to the others, as much as ten fold & more. These rejected cards are places in the HOT FILE & remain there until removed, denying use at that facility.
These washes are located in the same city in the upper midwest with a similar economic clientelle. Your thoughts Gentleman!
Frustrated!