Flir thermosight 536 - FLIR Systems Thermosight Pro PTS536 4-16x50mm Thermal Imaging Weapon Sight, w/FLIR Boson 320x256 (12 micron) 60Hz Core

I have had this product for about two months. It is my first thermal scope. The only issue I have had is that I maxed out its vertical adjustments when sighting it in and still shoots 3 inches low. I sighted it in at 100 yards using 220 grain sub sonic Remington .300 blackout ammo. It’s used in a 16 inch Ruger American. I’ve called FLIR several times and have not been able to talk to a rep to see if there is something wrong with my scope.