Well this is an odd one... driving along and one rear wipe clears the rear screen just fine.

 

Next time I go to clear the rear screen (and I have not stopped since the last one), the wash happens, the wipe happens, but the wiper blade skims over the screen without clearing anything.

Turns out there is tiny contact at the very edges, but nothing in the middle or at the rest of the wipe.

 

I'll pop it up the dealer, but I get the impression this is a wiper arm problem rather than a blade, as there is clearly insufficient pressure being put down.

 

Anyone else seen this?

I've had this in very cold weather where the wiper blade joints can freeze in position and not allow it to follow the contours of the screen - although this was at the front, not rear.

 

Is it possible that the first wash got some liquid on the joints that then froze?  Clearly, if it was a warm spring day where you are then you can discount this suggestion!

You haven't lifted it recently have you? I once had it on a previous car, the clip where it joins the arm had been dislodged slightly and prevented the blade bending back to the correct shape. Wouldn't explain why it happened mid journey though.

I've found the front wiper blades giving me no end of problems. Smearing, juddering, lifting off and not wiping properly at 100km/h. I had them replaced (for the price of a small island) and they're a lot better.