Wiper blades hitting?!

Yes ,it was my first thought. If you remember the 323 had them sitting with mortal grip and there was only thermal protection inside of the motor. Possible that links are not so strong now.
I forgot to say that there are plastic parts and the nut should be tightened without
excessive fanaticism.

I think the torque spec is something like 15ft lbs... I'm too lazy to look in the manual again but it's around there I'm sure

Bosch Icon = #1 all seasons! My :.02

Thanks all :)