+1 with Marty,
The factory clear is extremely thin and hasnt been able to 'build'. If i had a NIB, playfield strip and re-clear would be the first thing on the to-do list. Chris at High End Pins has also had a few Stern NIB's and Stern Playfields sent straight to his workshop for the same problem...so i dont think your alone on this one man. Hope you can get it sorted out
Timbo