I recently bought a Timbermule bandmill. It's made by a local company. It runs large pulleys instead of tires 13"2" blade. Anyway so far I've milled seasoned red oak without any problems. Today I tried milling green sugar maple. Every time I would come to a knot or a crotch the blade rises up and makes a thick spot in the board. I put on a brand new blade today, and tried to push the mill head with an even speed. What else could cause this problem? My only thoughts are the idler rollers I'm not for sure what angle to adjust them at. Thanks!