If you tumble more than 3-4 hours, change the media. Or put in some rejuvinator. Also, you can put in to much brass/media. I have a 20+ year old Lyman 1200. Put to much in, and it ''freeze's'' up. Everything just sits in the bowel and shakes, instead of moving around. Take out a handful or so, and it starts moving again. Never had any caliber brass, just sink to the bottom. If you loosen up or tighten the rubber gromet nut in the center, does that help. If I tighten mine up to much, it doesn't viberate as much. gypsyman