I swear F...... B.... at all my machines even though they are not on FB.
The dimpling on Stern playfields is normal under shiny light and does not affect play.
The magnet STDG  issue sounds similar to my Star Trek. I stuck a level across the playfield front and back and found one side about half a degree lower. I adjusted one leg and guess what! No more STDG.

Exactly right   you have to dial all new games in :) you can't expect to pull a game out of a box and expect it to be 100% beleive it or not even the old Bally/Williams games had issues out of the box and the good thing about new games like JJP/Stern a code update can fix most issues   geez I had to change a Rom to get ball save on my WH20 lol

120 games in on my Walking Dead and maybe 5 SDTM   Prison MB is a blast killing walkers is fun