I actually figured out how to fix this myself by messing with the .json files, but wanted to put it here both to help anyone else who might have this issue as well as in hopes that an update can fix whatever causes this in the first place.

I was working on setting up a table for a game I was going to play later, saved after I made a bunch of changes and added fog of war, then when I loaded it later it gave me errors saying that it couldn't load an assetbundle and some models because "value cannot be null." I spent a couple hours trying to figure out what was causing it until I realized that if I put the fog of war in to load last (after all other models and asset bundles, but right before the Decal Pallet) then everything would load without issues. I checked each Fog of War and deleted them all individually to see if one of them was bugged, but it just seems that if ANY fog of war is loaded in before a model or asset, then that item won't load.