Replace the hex bolts
Use toilet flange bolts or "T" bolts which will not twist in the slots because they have a wider area. Wax will also help as suggested, on any sliding parts. I like a 2 piece fence myself and that's what I have on my router tables. Suction off the back of the table using the dust collector works pretty well.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)