Having same problem
I was hoping you might have found a fix. My left rear turn signal started doing the same thing. Been trouble shooting the issue for about a week now and now my right has gone out as well. Before all the floods of "change the light bulbs" start, want you all to know I have some knowledge in Electrical DC. Anyway, I checked the bulbs, even got new ones and now I got spare bulbs. Any input would be great. My warranty went out some miles ago (about time) and I like to do all of my own work, mostly because I enjoy doing it and I am one of those fix it kind of guys. So far this is what I have checked. All fuses, bulbs and electrical paths. I have the same voltage on the 3 pins as you did and it is constant. The biggest problem I have is that I now have no break lights as the turn signal uses the same filament in the bulbs.
Jeffrey