How can I fix the Radio/CD player in my Toyota Prius 07 that malfunctions?

The Radio / Cd player play buttons on the unit very often in hot weather refuses to operate (on/off volume, selector buttons etc). It will work however on the steering wheel buttons.
Also this occasionally affects the alarm when its left and locked - off it goes without any reason?
When the car is cold / normal temperatures all is fine???
Any ideas please?