I have a Logan Platinum Edge mat cutter. After verifying with a carpenter's square that the squaring arm on my mat cutter is perfectly perpendicular with the cutting bar. I cut a mat, not putting pressure anywhere on the mat cutter itself while cutting. Board was flush with the squaring arm. Yet after "squaring" the new mat board I double checked the board and found a gap about 3/16's of an inch between the top of my board and the edge of the cutting bar (on a FULL size mat board).. I checked my board using the carpenter's square and verified it IS off. What could cause this?