Forst of all sorry for the late responce.

Depends where the ghosted piece will be spawned. When it goes darker it means that its position is inside the map boundary. TA has this controlled by "trackassembly_bnderrmod" convar being set to "LOG". Try disabling the protection if you really need to spawn a segment in this specific place or position it so that it is outside of map boundaries.

Good luck!