The locking ring "Easy Lok" on my XStream 1500 filter is becoming difficult to almost impossible to both turn to lock and then unlock to open. It first started last season and then this year the pool opening guys said they had a terrible time turning to lock and that I would probably have to buy a complete new filter. Last season lubricant helped a bit (silicon I think) but was still difficult. One one occasion I had a second person help me hammer it open with my rubber hammer. It is seven seasons old. Any suggestions?