FoRgOt To ChAnGe ThE .jSoN... Research before you @ me bud. Terrain materials.cs is still directed to Blank2, .json's are fine... And because I just know there's gonna be another issue with this map... it's updated with the fix...
Also, make sure SpawnedVehiclesFolder in the right mission group is checked can save. Thats the important one too
I clicked and dragged all the cars i spawned in out of the spawned vehicles folder and into the main mission group (just ignore the that folder itself has "cansave" off and "cansavedynamic" on). Right wrong or otherwise, it just kinda worked for me.