You hit one source right on the head, after 300+ flights I had a bearing shift in the wheel, result more gap on that set of brake discs compared to the other side, this was a source of pulling I had last summer. My Vampire has had very few flights off grass, I still have the original brake pads and tires, so things are getting pretty worn, but flex of the tire sidewalls has been increasing as of late, and they no longer are holding air so this will make the Vampire more sensitive to unequal braking.
Jim