I bought this filter used and have had no problems with it for about a month. Now all a sudden the impeller cover keeps popping up. I have checked both clips and they do not appear broken. I have triple check this so I do not think this is the problem. I am thinking that maybe the impeller has worn down a bit and causing the shaft to vibrate and cause the plastic cover clip to pop open. Has anyone ever had this happen to them before?? Thanks