I have a reconditioned Bosch 1590EVSK - pretty decent little jigsaw for basic breakdown of stock and rough cutting some curves. Tonight I was using it to finish-cut some plywood sheets that are too big for my tablesaw. Problem is I can't get the blade to cut 90-degrees to the shoe, or whatever you want to call it. I measured it after a cut and it was anywhere from 80-85 degrees at different parts of a 4' long cut. When I lock the red lever, the show still has some play in it. How do I set it up @ 90 degrees from the blade, and keep it in place?