Having unknown issue in unity 5 with lighting

I am making a tank game. The game is simple to look at, but the programming done in it is not that simple.
The issue is that when I start the level directly, i.e. not by main menu, the game will look like this below:

And when I restart the level or start the level via main menu, the scene looks like this:

The directional light is always on.

This is because you’re continuously baking the lighting. Don’t worry, as this will be changed automatically once you build the final game.

To fix it in the Editor, go to Window → Lighting → Lightmap Tab → Disable Continuous Baking → Press Build to bake the lighting.

Note that if you add more lights or make some changes, you have to bake the lightmap again.