This is quite a common fault with the high definition displays used with sat nav, it's a failure of the connections on the edge of the display, mine went the same way. New ones are expensive but I got one for a reasonable price from ebay but that to appears to be failing now.

Its mainly due to the heat the panel generates, it will feel quite warm if not hot when its been on for sometime and in hot weather and when you have the heater on its worse.

There is a discussion on the 406OC forum, repairs have been tried but not succesfully it seems. I believe if you don't use the satnav which I don't, you can use the more common and much cheaper non satnav display which is what I will be doing next time.

thanks for this link i just wrote to them so will se how they comming back

i not really use the sat nav anyway but the rest of the info for trip could be usefull also not look really nice as the display always missing some lines

anyway will sew how it goes and will update it

thanks