I agree with the "too small" blade comments! I use FD 2/0 blades, but only on the thinnest materials, 1/8" or thinner. If you've been using the 2/0s all along without much drifting, I'd recommend double checking your blade tension. It might be slipping just a little bit. Once you've got things set up to cut, tension your blade to where you normally do, then un-tension it and see if there is more slack in the blade than what you started with. I've run into this myself. Could be a little oil on your screws or blades or both! What ever you do, don't crank down harder on the thumbscrews! It'll only cause you more problems in the long run!