You probably have a bulb going bad. The filament in the bulb is broken and sometimes it makes contact and sometimes it doesn't.
one of the lights is not working
One of the bulbs is burned out. Turn on the blinker and look at the front and back turn signals to find out which one.
Your turn signals may not be blinking properly because something may be wrong with the wiring or fuses. Take your Harley to an authorized dealer to have diagnostic testing done.
When both of the turn signals (indicators) of a car blink simultaneously, it is usually because the hazard lights are turned on.
Check to make sure all bulbs are flashing could be a bad turn signal flasher
The flasher relay is defective. Replace it.
If both your left and right trailer signals blink at the same time there is something wrong with your wiring harness.
The problem could be in you flasher located on the fuse block . or the multifunction switch located on the steering column.
you need to replace the turn signil fuse
Could just be bad bulbs. When the bulbs go bad, even if only one side of a two lighted bulb, they blink fast. That or the flasher relay.
your rear bulb is blown - replace the bulb The turn signal blinks fast because the bulb is going out. That is also why the others dont blink.
You have a weak ground connection.