I know you are trying to help here, but this solution is not viable in big projects and it could takes days to do that. I told this because you used “[Solution]” tag. for me the workaround for this error was to download and install a free plugin called “RefreshAllNodes” and using that plugin i have refreshed all of my BP’s and removed Intermediate, Binaries,Saved files and making a build again. It should fix the error here. Also i suspected it’s caused by a corrupted variable in a level BP. So double check all level BP’s as well