This issue has been discussed over and over for the past few years. IMHO it seems that you are more likely to have the Zebra stripe issue if your radio was mounted in your car under hot sun conditions. Like any ¡°rule¡± there are exceptions. If I were going to use my 857 in my car I would take it out when not in use based on the volume of anecdotally reported trouble issues.. My 857D has been housebound for 10 years or so with not problems.
I have my 857d in the car for the past 8 years.? Head is on the dash board in the direct sun.? When the rig is not in use a cap is put over it to keep the sun off.? ?The rig is mounted vertical on the center console near the passengers feet.? Rig stays warm from the heater in the winter and cool form air conditioner in summer.? ?See my QST article 2010 January page 46 about mounting the ATAS on a magnetic mount.?