I noticed while playing on official and my local server 1.13 PC normal build game version that when you leave any car running and in neutral and you exit vehicle that tail lights/Position lights goes off. And when you restart lights by turning them on and off again that your position lights are lighten up again.
I noticed same behavior for:

1. ADA 4*4 [Lada Niva]
2. Olga [Volga]
3. Gunter[Golf 1]

Will test Skoda and Praga truck and I will update this post with findings.