With a quick Google search, a powdercoating forum thread comes up with this quote (from 2009): "...all the veins need a clear coat for outdoor use. If its for indoor use and it isn't touched or handled regularly you can get away with out clear."

While my ACNC still looks great, my used AMH came with worn vein, and RZ looks susceptible.

Sounds like vein coating may not be ideal for pinball, but hopefully some clear coat solution works, as I really like the look/feel of it, particularly the heavy vein on ACNC.

What I quoted wasn't related to pinball, but may explain why we're seeing issues.

Clear coat these days also isn't what it was, so perhaps taking some time to figure out, but Spooky is aware and trying to address it.