My Lyman 600 which I converted to 1200 by adding the larger bowl is still going strong and I bought it in the early 80's. It's been used a lot so I can definitely recommend Lyman. I have purchased the Dillon CV 2001 model as it has a 12 1/2 quart bowl that will do 500 30-06 cases at a time. If it's too large the Dillon CV 500 is smaller. The CV 2001 really moves and shakes the media and is very quick cleaning brass. It'll do in an hour what it takes 4 hours in my Lyman. However I've only had it for approx. 2 years so I can't give it the same long-life recommendation as the Lyman that has lasted approx. 20 plus years.
Have you checked your Lyman bowl to make sure it's tight on the base? It could be loose causing the bowl to not vibrate correctly?