Hi Dorisgao,
I think the problem you’re running into is that your characters location is being set every frame to be on the spline.
So I think a solution would be to have the ‘scene root’ follow the spline (like it already is) and change the location for certain objects in your pawn/character.
I tested this for just the camera, but It should work the same for a hierarchy of parent/child objects. (A mesh with a springarm child with a camera child for example)
Welcome to the forums, let us know if you have any more questions about this!