How about removing the blade and remounting it on the saw........while the blade is off inspect the arbor/shaft/threads/spacers.....try moving the shaft:up/down/side-to-side/in/out...........clean it all up before remounting the blade...........
I usually find the nut is loose.........a little crud in the threads prevents tightening......a burr on the spacer/washers........Forget one of the washers?......... or some other small problem.............Something more post back........doug