This was the solution to my issue. There was broken redirect in projectroot/config/DefaultEngine.ini
For anyone struggling with this open up the DefaultEngine.ini file and look at the list of redirects.
It will have the header [CoreRedirects] and a list of items like
+ClassRedirects=(OldName=“”, NewName=“”)
+PropertyRedirects=(OldName=“”, NewName=“”)
+StructRedirects=(OldName=“”, NewName=“”)
Ctrl+F in that file and make sure you have no loose ends for the broken blueprint class in question.
It can be setting your class to an invalid class here so just make sure.
Hope this helps someone 