I'm trying to create a sled. I found a great Mpc on another thread. It calls for a 14.5 x 44" board. I cut a a piece of 3/4 ply to use and started my process. I loaded the board and when it ask to stay under the rollers, yes and then it says "load board". But the board is loaded. So I pull it out and find it has a slight warp. Go cut another board, this time a nice straight flat mdf. I load and the same error. So I throw a small 4x14 in and run a quick keyhole to make sure the machine is running. No problems there. I also vacuumed and blew out the machine taking extra care to clean the rollers and then lube everything up. I also checked the pressure and it reads 80lbs. I Reload the nice flat mdf board and no go. I pull it and run another smaller carve with no problems and load that big honker board again and no go. Now, I'm thinking I don't want this problem every time I use a sled. I went over the board with a fine tooth comb. It is flat, the edge is clean. I can't find a thing wrong. Any suggestions before I cut up yet another cabinet grade sheet of plywood