I noticed watching the meshes for example the display case will be vibrating left but the glass at the same time vibrating and moving to the right , same as a Z , so figured this must be the issues ,It's cause the graphics engine tells the gpu where to draw each object, and where the camera is - and the gpu combines those. So you have +15002 for the object, -15000 for the camera, to get something 2m away from the viewpoint.
The gpu doesn't know things like "needle is child of dashboard is child of cockpit is child of car," it just gets the coordinates of the needle object. So it gets less accurate the bigger the numbers are (floating point precision)
On some shaders/gpus it'll even transform every vertex individually in which case entire objects get wobbly at a distance. Mostly you just get it combining object+camera and then multiplying that onto every vertex though, so they're pretty consistent, it's just 2 differently positioned objects that end up z fighting (if object origins are identical, the transform's identical and they move together - so one good tip is make all meshes of a car have the same origin unless they're movable).
Mostly it's just there because 15km out is about 3 times as much as they needed for any content they planned to include, modders adding bigger tracks is not really their concern. Nordschleife gets closest of stock content cause it's the largest track.
but actually was discussing it days ago with Ilja Jusupov the creator of content manager and its actually a shader issue that causes it , he wrote all new shaders and the issues are way less visible , so maybe its something kunos can look into at some point reworking and optimising the shaders , but anyways its a strange thing to watch when stood still and the car feels like its gonna get sucked into a black hole