My brake lights do not work. Bulbs are fine, fuses are fine any ideas? on 2000 Chevrolet Venture

My brake lights seem to intermittently not work. Sometimes it is just one side and sometimes it is both. Sometimes they work fine. I have checked fuses and bulbs. Any Ideas? Do you know what it might cost?

Asked by for the 2000 Chevrolet Venture
Sounds like wiring or socket probs since the intermittent one side or both. There can also be a prob with turn signal switch since the brakes work thru it because the brake lights work when turn signals are on. May need to take to qualified shop and have checked. The thing that will make it hard is the intermittent part of it.