For anyone who is interested the Kiss pinball at Timezone now has a few small dimples appearing mid playfield to the left. Too small to photograph.

I can't remember who mention that their ACDC actually smoothed out over time but there could be something in that. If you check out the Ironman next to Kiss at Timezone it looks fairly smooth, almost like all the dimples have joined together and other than needing a clean it plays quite nice.

... lots of small dimples fixing itself over time, sounds like the clearcoat is soft.  Nino's issue sound like its to thin.  I think there are two things at play here, as Nino suggests.  Nino's TWD sounds like it had a production problem - somebody probably forgot to apply the second coat to it!