I wouldn't change the switch as a first step. If you feel like changing something, change the turn signal flasher can under the dash. They act goofy once in awhile.
After that, with the lights on and the right signal selected:
Take a jumper wire. Touch the light bulb base right where it meets the glass. Touch the other end of the jumper to a known good ground. See if this changes anything. Try it on both the front and rear bulbs. This jumper will bypass the socket ground and body ground and directly feed a ground right to the light bulb.
After that, with the lights on and the right signal selected:
Take a jumper wire. Touch the light bulb base right where it meets the glass. Touch the other end of the jumper to a known good ground. See if this changes anything. Try it on both the front and rear bulbs. This jumper will bypass the socket ground and body ground and directly feed a ground right to the light bulb.