Issues with material library in world editor

I've been having many issues with the world editor's material library. Firstly, the delete button for any created material crashes the game. Second, any texture files selected for a material don't save, so when I try to apply and select, the material defaults back to the warning material. Is this a common issue or this on my end? The "main.materials.json" file in /art/terrains/ should be correct, so I don't really know what's going on. This is my first time working with the new world editor, and I'm pretty lost here, so any help is appreciated.
After selecting each texture:

After applying:

main.materials.json in art/terrains/ :