Try to remove all materials from meshes and test it.
Have you tried to test without platform above?
Also, remove material from landscape/floor and set landscape position to 0,0,0
EDIT: set fixed FOV for your camera to 90 (also test with various values), do not change FOV or spring arm length while moving.
Try with camera lag enabled too. It’s hard to debug this kind of problem so you need to try various solutions.