Seems like there is a chemical reaction going on with the solvents and the brushed aluminum coating. Just by looking at it and from experiencing this when painting auto parts in the past I ran into similar issues as this. Just my opinion.
2015 here, mine has done the same thing. It doesn't peel or anything so I dont sweat it. Wife props her dirty shoes up there all the time anyways so whatever. I"ll wrap it in vinyl one day and never sweat it again.
Well THANKS for nothing. I hadn't noticed the cracks until you brought it up and I looked close. Now I'm sure it will bug the hell out of me until I get it replaced. At least I'm still under warranty.:caked: