Before we consider making controller changes, is the user on the "a" or "b/g" band? Either way, find out what access point he/she is connected to and run the following commands:
show ap debug radio-stats ap-name <ap-name> radio 0 advanced | include Resets,Busy,intvl,Fail,Retry,Changes
show ap debug radio-stats ap-name <ap-name> radio 1 advanced | include Resets,Busy,intvl,Fail,Retry,Changes