My DH solved the problem by wrapping duct tape where the bike & the hitch make contact. No problems since, but that mark bugs me every time I see it.
You didn't try to touch it up? I was thinking about taking some white gloss enamel spray paint and spraying it on a paper plate and then lightly brushing it on with a brush. It may look worse.

I did write an email to Saris customer service to let them know about the problem. I think they need to be aware and also I'm scared to use it on a long distance now. You may want to notify them as well.