Hey JB,
You didn't mention it so I will assume the front Left motor is working OK?
There was another Poster recently who had LED issues. He found that by pressing or flexing the ESC a bit they would work as long as he held the pressure. This points to an issue on or with the ESC. Most likely a solder joint or other loose connection somewhere.
There's a 4 pin connector which carries the LED and motor speed PWM signals from the main PCB to the ESC. Make sure it's properly inserted. Maybe remove and inspect, then re-seat it.
I would try the flexing as well. If it is intermittent you'll have to replace it or search for and repair the problem if you can find it and have such skills.