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I'm on the latest firmware and this has been there since the purchase 1½ ago. So either live with it or get another car.

Okay, although not a fix but I found a workaround similar to Dolph's suggestion but with fewer clicks which has worked for me.

I have sat nav and DR preset radio channel displayed on home screen as per screenshot 1. While on this screen, tap on the radio channel display name. This will bring up the screen displaying 6 preset channels as seen in screenshot 2. Now turn/scroll the media control wheel on the stalk which should change the channel. Now press the back button to return to your first screen which should fix the problem (at least this does for me).