Hi,

This is not actually bug, but rather a missing person item.

In single player, when you winch a truck, nobody is inside the second truck...

Here I'm wintching the B66, and nobody is inside the cabin...

EDIT: we can't really see him because of reflexion, but there is someone in the cabin of the first truck. But there is nobody in the B66.

Hi there, is this in multiplayer?

The idea of winching a vehicle in single-player is that you're getting out of the truck, turning on the engine of the second vehicle, and then going back and towing it. There wouldn't be a second driver.

It is in single-player.

However, even in singleplayer, the wheels of the second truck can turn left or right to follow you, and you can ask the second truck to accelerate.