The first thing I would do is look at the cut in the board you just made. If it looks like the gap is narrower at the end of the board than where you stopped cutting then it's the wood. Another simple check would be to get a straight edge and place it against two teeth on the blade extending past the riving knife. Do it on both sides of the blade. The straight edge shouldn't touch the riving knife. Instead it should have an equal gap. Make sure to do it the full length of the riving knife (while not as bad as a splitter) you want to check that it's not twisted compared to the blade. That being said I do agree with the others about calibrating the saw. When you do don't forget to do it with the blade at both 90 and 45 degrees.