I have just built a new router table for my constant speed Porter-Cable router. It is working wonderfully except for one big issue. I am putting together rails and stiles for some cabinet doors and have noticed that the router slips down ever so slightly as I route multiple pieces. I have ensured the bit is secure and that the router itself is tightened as tight as I can get it by hand. Does anyone have any ideas on what could be causing this? I appreciate any help!