Try and take the wiper assembly apart, clean and apply new grease at all joints.
You have to take of the wiper arms, and the plastic cover under the windscreen. 2 minute job. The rest is a bit more fiddly, but should be quite easy.
The reduced friction of the cleaned and lubricated wiper mechanism could actually make your wipers behave.
If this doesn't work, at least you'll have solved the squealing. And maybe other users have more ideas.
Cheers,
Ulrich