If you tighten the stop pin screw before inserting the blade assembly, you can still crimp the outer edge of a washer. This is not a pinched washer, per se, but it can develop a little burr.
If you can't get it settled by reinstalling the bushing, have a look at the outer circumference of both washers, especially the large. If it's out of flat, you can knock it back down on ceramic.
I tighten the rear back spacer screw, but back off the tension on the stop pin a smidge. Hand tight but not cranked down.