I picked up an old craftsman radial saw off Craigslist and have thoroughly read the instruction manual and alignment procedures; however, it seems that the arm is stuck in the 90 degree position and will not swing for miter cuts. The release mechanism is the knob in the front, but turning it all the way in or out makes no difference. All of the other components work correctly, and according to the manual im not missing anything. I see no obvious restrictions to its movement either. Has anyone encountered this before?