Today, the wiper on my 10 year old c180 started stuttering across the windscreen during heavy rain... It came and went that way for about 30 minutes, then there was a 'pop' and the arm started wiping again.

However, it now simply wipes in a crescent shape, it should wipe in a sort of 'cam operated' up and down crescent shape.
Because of this, the wiper now hits the front windscreen pillars at the full extent of the right and left wipe.

The wiper arm can now also be pushed in and out.

I haven't had a proper look (to dark and wet) but has the wiper arm popped off part of the driver shaft or whatever? Is this fixable? is it easy/cheap to fix?

thanks for any guidance