I've been working on a mod for which I need to make some terrain edits to the Fort Joy level in Origins, but every time I try to load the mod in game the terrain reverts to an unedited state.

The changes made by the mod load consistently and repeatedly in the editor

Heres what I've tried:
1. Selecting the terrain in the editor, right clicking, and opening the terrain for edit, then saving (I didn't open it for edit BEFORE I started using the sculpting tools in the terrain panel because I'm an idiot, but it's too late now...)

This returns an error "cannot open file for write .../data/mods/origins/levels/FJ_FortJoy_Main/Terrains/_merged.lsf" (thats not the exact filepath, except for the '_merged.lsf" part at the end, I'm just trying to convey the broad stroke, which is that the editor can't open said merged terrain file for write, and yes Ive tried running it as admin)

2. Moving the DOS2 directory straight to C;/ (to ensure the file path being too long wasn't the issue)

3. Deleting the terrain (without opening for edit, the editor just tells me it's locked by source control. With the terrain opened for edit, even when I save and reload the level the terrain still shows up in editor with the modifications I made, and in game without them, so this does nothing)

4. Placing a copy of both the _merged.lsf and all files in in the terrain folder with the guid of the terrain in question in my mod and an origins directory I made in the defed data folder explicitly for the purpose of seeing if it would help, both at the same time and independently.

As a side note there is no actual file generated for the GUID of the terrain in question in the levels/FJ_FortJoy_Main/Terrains subfolder of my mod, nor is there one generated in the same subfolder of the origins mod by any of my attempts to save these changes, so I'm somewhat baffled by the fact that the editor seems to retain them, and even more so that despite them being retained they don't show up in game.

Not really sure what else to do other than slap my face against the wall in frustration, if anyone has dealt with this or could offer suggestions they would be greatly appreciated.