Sorry for the delay. What do you do when you get this error?
It is caused by a script requesting a resource that the current use don’t have the necessary privileges to access. Do you use for example vLookup / SPJS-Lookup or cascading dropdowns and have the “child list” in another site?
If you get this when DFFS loads, it might be that the user don’t have rights to access the “SPJS” document library where the DFFS files are located.