I don't think there's a "read only" in lite-C (EDIT: oh, C-Script... dont know anything about it anymore), you can overwrite everything. You just shouldn't, normally
level_ent normally is changed automatically when it needs adjustment (like when entities leave the level boundaries) but I've had trouble with it in the past.
You might want to check those and let's say camera.xyz.


You *can* scale terrain but only immediately after creation, not a frame later (as it's turned into chunks). - Btw. any reason to not use chunked terrain?
Try saving your terrain with filename + _n, like myterrain_n.hmp. This is or was a hint to not use chunked terrain as well, might help.