HorrorUK on "Permalinks continually stop working"

I'm having problems with my permalinks continually not working.

I get a 404 page come up on, for example, my contact page, so I go to Permalinks and save them, which then fixes the issue for a day or two, but the problem reoccurs, and I have to do it again.

Is there a way to stop this from continually happening?

the permalink I'm using is:

/%category%/%postname%/

Thanks