For some reason, when I child an object to my FPS controller’s camera it doesn’t move up and down, only left and right. Has anybody else encountered this before?
The standard FPS controller has two MouseLook scripts, one assigned to the camera and restricted to rotation in the vertical plane, and other assigned to the character and restricted to rotation in the horizontal plane. These restrictions are defined in each MouseLook by the Axes field shown in the Inspector. If you child an object to the camera, it will move only in the axis enabled by Axes. Check this field to know which axis is enabled.