Signal Strength and Quality

I am an installer of Wilson Pro cell extenders and recently installed the 4100 amp in a local hospital.  We have an antenna located on the roof and have good signal but the customer keeps having dropped calls or cut offs.  Wilson seems to think that there are power surges in your signal that interfere with the amplifiers ability to adjust the signal.  Is this a potential problem with vorizon signals.  The location is Bismarck ND 58501 and the street address is 7th St and Rosser.  We have trouble shooted this for several months, replacing the amplifier, and other components.  Just wondering how to determine that a cell tower is operating correctly.  We will go for 3 weeks without an issue and then suddenly it happens again consistently.