Ford Ka Rear Windscreen Wiper Loose?

The rear windscreen wiper works OK, but doesn't stay in place.

Once I turn it on it moves from starting position to dangle downwards and the wiping action wipes the lower half of the rear door and not the window.

I can't position it manually as it just swings down under gravity again.

I believe the problem originated when the wiper was forced out of position by a monkey.
(You get what you deserve driving through monkey enclosures)