The most common cause for this is interference from another electrical product in close proximity to the shower other known as electromagnetic interference. The difficult part however, is ascertaining exactly what's the cause.

The most common are:

• LED Light adapters
• Adapters for mobile phones or similar
• Television transmissions both analogue and digital.
• Radio AM, FM, and Satellite.

In the first instance, try moving the radio antenna around at the back of the shower to see if your signal improves. This is the wire that comes out of the back of the control panel. If this fails, it's a case of trial an error with switching products on and off until you find the interference. 

We stress, this is always 100% the issue, it's not the control panel that is at fault, so requesting a replacement will not solve the issue.