The camera is meant to be always moving on the same ZX plan, but if you want to prevent it from sticking at y=0, you can edit a few lines. For example in CameraPerspective.cs
in the FocusCameraOnGameObject() and HandleFocusAndFollow() methods, remove or comment out these lines:
// offseting the bounding box
float yOffset = b.center.y;
b.extents = b.extents.SetY(b.extents.y + yOffset);
b.center = b.center.SetY(0);
Please note that the camera's center point on the floor is not meant to be changed in Y, so you could have glitches.
Hope that helps,