Problem with mouse look and second skybox cam

Hi everyone, I'm having a problem with a secondary skybox camera setup, currently I have one main camera (for the first person view), and a secondary one that manages the skybox/terrain in the distance.

Most of it works as it should, except when I move the mouse around, it appears that the skybox is responding to wherever the mouse is looking, as opposed to staying where it is. For example, if I look upwards, the horizon line of the skybox also moves in relation to wherever the player is looking.

The only thing I can think of is that there is perhaps something odd happening with both the built in third-person controller and a secondary camera?

Any help would be most appreciated, all the best!

-D