Indesciminate scanning of audio system

Hello everyone. This is my first post, been a 2012 Prius, type III owner since September. Have researched this forum and it is loaded with many helpful solutions and upgrades to various problems, but I haven't been able to find an answer to this:

I have a audio/nav system. I will be listening to a fm radio station and all of sudden it begins scanning the stations. I have discovered the only way to stop the scanning is to push the Volume Control on the steering wheel. All other buttons on Audio/Nav are unresponsive. The whole thing freezes up. when I depress the steering wheel button the audio just stops at whatever station it is on and continues playing. Then about 1-2 miles later it starts all over again.
Anyone else have this problem and found answer????

 

I see no one could answer this.
I thought I would tell everyone what happened.
I fabricated my own sun-shield out of cardboard. It fit "perfectly" by sliding it into the space between the NAV buttons and screen. EXCEPT (which I was unaware of at the time) for the space where the SEEK button is located. The cardboard was holding the SEEK button down, but intermittently. Once I determined this was the problem, a simple scissor cut to that part of the shield so it would not go into the space solved the problem.