When I restored my Space Odyssey I had those raised dimples under every playfield post too.
Many of them were quite pronounced, and rather than block sanding them down I pulled out the Dremel with a small grind wheel on it and used that to take the bulk off of the top and help bring it back down somewhere closer to the rest of the playfield surface. After that, I then block sanded the last bits down to get it to where I was happy with the results.