This involves any world updated to 2018 using substance designer materials and would get this error:

ERROR: Built-in support for Substance Designer materials has been removed from Unity. To continue using Substance Designer materials, you will need to install Allegorithmic's external importer from the Asset Store

Should be fixable on VRChat's end as for my projects files is using the importer and loads the scene no problem and i am sure its fixable on VRChat's End.