You have the two bulbs in front. The lower is on with the park lights and headlamps. It will flash with the signals in time with the top bulb which is only a turn signal. Then you have the back bulb above the brake lamp behind the yellow lens.
If one of the bulbs on the same side of the car is out or has a bad connection, it causes the flasher circuit to double the flash to get your attention that a bulb is causing an open in the circuit.
Recheck your bulbs front and back. Check the plugs; clean and tight.
If one of the bulbs on the same side of the car is out or has a bad connection, it causes the flasher circuit to double the flash to get your attention that a bulb is causing an open in the circuit.
Recheck your bulbs front and back. Check the plugs; clean and tight.