Good question. I've wondered the same about one of my Z3 that continues to have tracking problems even after a trip to the factory. As I recall, Swarovski recommends the lightest scope ring tightening of any scope I've played with.
I have wondered on occasion whether Leupold's lightweight tubes may be the reason there are so many tracking issues. It may be that the slightest ring misalignment causes the erector to bind up. All I know is I grew weary of the hassle of zeroing a Leupold scope. Whatever the cause, I wish they'd address it and not continue to try to blow smoke up everyone's ass.
