If the aperture on your PENDULUM sight is having trouble swinging freely during use the problem can be caused by the rubber bushing on the threaded portion of your PENDULUM swing stop screw. This bushing can become deformed and spread out enough to contact the sides of the swing stop cutout, creating drag and impeding the action of the sight.
Please fully remove your swing stop screw and examine the rubber bushing for deformation. Sometimes when placed away, especially for a longer period of time, it can make sense to not fully tighten down the bushing to help retain its original dimension.
Lastly, if the informartion above does not fix/help please give us a call and we’ll be happy to help.