I had my Vortex love shaken recently. I installed a new 4-16 on my FN and put up the best groups I've ever shot. Then I did a tracking test and one shot was very far off of where it should have been. If it was me, it was the only shot I made that day that wasn't amazing. It was very far off though, like 3-4 inches from where it should have been. I dunno. I have to retest.