Not placing a new cartridge tray close enough to the location of the previous tray.
Aligning the needle to the cartridge, rather than aligning the camera to the cartridge.
Machine vision camera is out of focus or improperly calibrated for the current hardware
Align your cartridge tray front edge flush with the cartridge platform front edge. If it helps, you can draw tick marks on the left & right sides of the cartridge platform, or use overlapping rubber bands to create an alignment grid and ensure consistent placement from tray to tray. (*Example pictures below)
Use the "Concentric Jogger" to locate the first/last cartridge by moving the platform to the left/front edge or right/rear edge respectively, then click the "Align" button to align the camera to the cartridge.
Perform machine vision camera calibration [Page 7 of user's manual]