My car dealership now admits they were having problems with their website and have now corrected them. The problems seem to have affected the car manufacturer's website as well. Most likely the manufacturer provided buggy software and updates to their dealers, thus affecting many dealer websites.
I am no longer seeing 6-column display problems in either NM 27 or NM 28. I have made no changes to my system other than periodic New Moon updates.
This explains why some of out helpful friends were seeing bugs on some system setups, but not on others they tested later.
My thanks to you, Roytam1, and to your supporters for your responsiveness to me. .