Our skimmer tray keeps coming out of its recess. Has anyone had this problem, and if so how can I fix it? I could put something heavy in the tray, but that would block the water flow to a certain degree. Our pool store said that it is the right skimmer tray for our pool. It just keeps popping up and than it sits in the skimmer with a big gap allowing big stuff to pass by and go to the secondary filter tray. Thanks.