I think so. Mine does the same, always has while I've owned it. Also sometimes it doesn't park in the same place each time, can be 2 inches up at the very end, still kicks down to the original place before the sweep.
If it wipes the window it's doing its job, I wouldn't worry
I replaced my front motor the other day and when I turned them on, they went in the exact opposite direction they were supposed to. Turns out that the arm that connects to the motor has to be at an exact position between two marks on the frame while in the resting position.
Could the rear motor require the same sort of thing so that it does not behave in this way?