Weird: I just had the same issue on my ‘14 an hour ago. Coming home from dinner and when I signaled for a left turn the dash display told me I had a L-R signal light out. I pulled into the house and removed the taillight housing, completely forgetting that I had the LED package. Once I realized there was no bulb to change I plugged everything back together and tried the left signal. Every LED was illuminating properly and the signals were flashing at the normal speed. The dash signal indicator was still flashing rapidly and the “Left Rear Turn Signal Light Out” message was still showing. I checked both front and rear signals and both were still flashing normally. Then I looked at the dash again and everything was back to normal. Weird.
Hopefully I just had a dirty connection, but I’ll be waiting for it to happen again. I’ll probably clean all the taillight connectors tomorrow just for giggles.