I am having a problem with my 404! Fir some reason it starting leaking about a week ago right by the left latch. I took it apart and cleaned the O-ring and re wet it but it is still leaking. The filter is only about 6 months old. Any idea's? I remember on my old canister the instructions said something about putting grease on the o-ring but in the Fluval instructions it only says to set it before installing it.