Well, I took the left turn signal out again. I didn't notice any real "strain" on the wiring harness, but after removing the bulb I was able to push the red wire into the socket a little bit. Seems that the spring mechanism in the socket was sticking and probably making intermittent contact with the bottom of the bulb because the red/black wires were curved right at the housing and preventing the wires from slipping through the rubber boot. I added a touch of oil to the wires/rubber-boot and straightened out the red/black wires to let them move freely. Funny, I installed the original bulb that I replaced a few months ago to see what would happen. It worked just fine all day today. I'm going to run it like this for a while and see what happens.