Intermitten slow blinker?

  00 Buick Park Avenue, 1 blinker works fine. The other blinks slow or will just stay solid lit up. The switch behind the dash clicks slowly. But when the blinker is solid, the switch clicks like it should. There are 4 bulbs for each side (2 front 2 rear) when the blinker is turned on. The 2 in the rear flash together and the 2 in front alternate. All bulbs are working. When I turn on the hazards, (without the blinker on)1 side operates normally while the slow side still flashes slow or just lights up and stays on. All bulbs are working. I hope all this makes sense. Any idea what could be causing this?