What is this Substance error?

“Substance: invalid assembly, cannot import file” pops up when I try to import an SD6 SBSAR file into UE4.13.2 and fails to import. I’ve fixed what I thought was causing the problem but it still persists. Older exported SD files work fine. I’m guessing it has something to do with compatibility issues between UE4.13.2 and SD6. Has anyone else had this pop up? I’ve changed my compatibility mode to Engine v5 and it still occurs.

UPDATE: I have found out that I can import the files into a new project but won’t import into the project I’m working on.

UPDATE 2: I’ve practically destroyed a copy of my SD material to it’s most basic form and I’m still get this result on the Output Log. I have no idea how to fix this.

LogFactory: FactoryCreateFile: SubstanceInstanceFactory with ReimportSubstanceFactory (0 0 …/…/…/…/…/…/…/Desktop/Forbidden - Dark Rose/Wood Panel/Test Export Wood no NRM blend.sbsar)
Substance: invalid assembly, cannot import file.
LogAssetTools:Warning: Failed to import ‘…/…/…/…/…/…/…/Desktop/Forbidden - Dark Rose/Wood Panel/Test Export Wood no NRM blend.sbsar’. Failed to create asset ‘/Game/Manor/Test_Export_Wood_no_NRM_blend’.
Please see Output Log for details.