What I have found through the years, is, when I was younger back in the 80s I thought a lot of my cars had little ramps that pulled the windshield wipers up in the air so there was no load on the wiper blades. Nowadays, it seems like all the cars I’ve owned don’t have that anymore and they sit there with spring load on the whole lad assembly. That load pushes the wipers so they bend 60 to 75 degrees. Every cycle movement they have to rotate over instead of staying somewhat stiff and only getting movement by the little 6 mm of the wiper blade themselves. Now you have the whole blade assembly rotating, and that clunking is just the whole blade assembly rotating 120 to 150 degrees. It’s like they did not want to design the dual cycle of coming off the ramps going on the windshield and then wiping without hitting the ramps and then when you turn off the wiper it cycles to the second cycle and place themselves on the ramps to load the wiper blades I have no clue if you guys with BMW‘s Porsche‘s Cadillac and Lexus have this but all the commoner cars I’ve driven, I always have to live with bad cheap wiper designs