I've had the same thing with 2 of my DeWalts and one of the Excaliburs, so not uncommon. Another thing that can make your cuts different from top to bottom is feeding the wood too fast, and "pulling" around corners and curves, instead of pushing into the blade. Both of those things will cause the cuts to be slightly beveled. Both are also great ways to break blades or pull them out of the blade holders. Sometimes this hobby takes patience!
Nancy