If your unit is equipped with removable collars: ensure the threaded collar is seated all the way into the body, sitting flush with the top of the body. Press along the bottom inside of the collar to ensure it is fitted into the groove in the bottom of the body all the way around. If issues persist, remove the collar, clean the body and collar and then dry out completely before replacing it. Thread the globe in so it is snug. If the globe is difficult to thread in, use a small amount of vegetable oil on the threads.
If your unit has solid plastic collars that cannot be removed, please contact customer service.