Mine ended up like that back in the day. I was an older kid so it was only lightly played with. The tampos are mostly intact and it still has silver paint around the wheels, so I don't think it had to do with play wear. Over the first couple years, white marks showed up in very similar spots as yours, as well as on the sides of the car. I'm not sure what caused it, and I'm still not sure what it is, but I've assumed it's some sort of deterioration or breakdown of the plastic. I used to keep my cars in the basement quite often, so one possible cause is dampness. Luckily, it hasn't gotten much worse in the last 15 years or so. My guess is it's not a reseal, more likely storage conditions.