Hi I don't know why but my windscreen wiper has develped a really annoying knocking when I'm going over 50mph, the right hand wiper makes a loud knock every time it goes up and down when above 50 but below 50 its fine.

What should I do? Replace the wiper?

 

Depends on where the knocking is coming from, but replacing the wiper could eliminate the wiper as the source.

 

Check and see if the metal came out of the blade. There's two thin strips of metal in each blade and one of the came out and was smacking my sunroof. I thought I was getting pelted with stones. Just slide it back into the blade and make sure it locks in place.