Upon attempting to load my map in radiant, i'm confronted with this error. This happened to a previous map where I deleted the map thinking it was corrupt and made a new one. Next day i try to edit my map i get this error again. I tried verifying the cache of both BO3 and BO3 mod tools with no luck on fixing it.

If anyone has any possible solutions it would be much appreciated.

Guys I have an answer to this!!! go into the .map file of your map and copy the entire coding, create a new map in the launcher and go to the .map file of that map, copy your map code into the new map code and load the new map as your old map worked for me.

In short.

1. Open (yourmap).map in any code editing program, e.g. notepad
2. Copy ALL code from this file
3. Create new map with the mod tool launcher (name it anything you like)
4. Open the new map with a code editing program
5. Paste your original code into this new file and save it in the original location but under the new map name.map
6. Load radiant and load the new map instead of the original map
7. Have fun working on your map again

Found this on the steam forum, might work, havent tested it myself yet
https://steamcommunity.com/app/455130/discussions/0/350543389012260899/

Also, youy could look into this folder "Call of Duty Black Ops III\radiant\autosave_backup"
 and restore from there, your maps are located over here "Call of Duty Black Ops III\map_source\zm"