Identical cars in traffic after installing modifications (Grand Theft Auto 5)

I put on any mod and the same cars start rolling around the city, you go into any parking lot, there are 8 identical cars, and even some of them are too bright colors.
I tried to install a clean game and everything is normal. I remember that in GTA4 when changing cars, when there were only taxis and so on ... I would like to know from everyone? and is there a way to get rid of this?