Configure the display to show Digital Error Count. Display Options/Customize. When receiving a signal it should be something like less than 10. If it suddenly goes up it means that you are interfered by another transmitter and you could try IFX on that particular frequency or change the filter type for that site to try and get a steady signal. If it is a conventional system and not trunked the filter settings are under the department settings and will affect that whole department.
/Ubbe