Hard to know if you're doing anything wrong. I've noticed it's not unusual for the QL to wear more than the rest of the chain. I don't worry about it much. Only thing I can think of is that the QL might not get lubed as thoroughly when installing and creates more wear on that pair of links so even a new QL won't eliminate the difference but, that is just my completely unscientific guess. Also, most chain checkers will show more wear on your chain than you actually have. Use a ruler to measure as a backup to your checker.