I've done numerous tire changes on the bird but never noticed this before...
facing the front of the bike, there are two thick brake lines that travel down the side of the fender on the right side. One of those brake lines pushes in on the flimsy fender, causing it to gently rub the tire. You guys should at least make sure this is not happening on your bike.
From the front of the bike, run you fingers around the inside edge of the tire. When you get to the inside edge of the fender, the clearance should be the same on both sides. In my case, the right side has a paper thin clearance while the left has at least a 1/4 inch.