Frustrating replay bug

This is a little weird. When I make replays and when I exit and come back to beamng and play the replays most of the traffic is gone. Why does it do that?
It makes it impossible to make BeamNG videos.

 

the traffic spawns and despawn around your driven car for performance reasons. you have to park your car in the area you wanna film if you want traffic there.

 

Thanks for the help.

 

Is it because of my cache?
I have ~15 gb of memory
Yeh I know wtf why do I have so little space