[Cross-posted from JJP forum]
I was at the Southern New Hampshire Pinball Club last night and noticed on their Hobbit a bit of scuffing of the playfield surface around the troll mechanism openings. The rounded corners of the metal flaps on the troll mechanisms had burrs along the bottom which were likely the cause of the scuffing. A few strokes with a flat file along the bottom edges of the flaps removed the burrs and left the underside of the flap much smoother.
Tony