1989 300SE Driver's side wiper problem.

[vince300se]

Hello,
My drivers side wiper arm moves past the window then hangs up. It was working fine but now it appears that something is either wrong in the linkage or that there is some sort of adjustment to tighten the arm to the motor. The passenger side works fine. And I can move the driver's side where it begins to work again, then works for 1 or 2 wipes, then it goes beyond the wipe range and locks into the windshield channel. Does anyone have any thoughts on this? Is there a linkage mecnahism? Are there two motors? Is there a way to tighten the arm to the motor? Any input will be greatly apprecaited. Thank you.