how to make an adjustment to a powercraft tile cutter?

Hi, I purchased a powercraft precision tile cutter from Aldi's. It worked great at first and cut tile and granite beautifully. Now it leaves cutting marks on the tile and chips the edges badly. It is an overhead cutter and the blade does not seem to align anymore. I have tried changing the diamond blade but no improvement. Is there an adjustment that can be made. I have lost the original instructions and cannot find any online. Thanks Mandy