Package without source

I need to provide a way for my producer (and artists and designers) to build a package without source code. I have prebuilt all the dlls required, but it’s now complaining…

Could not parse Engine Version from ObjectVersion.cpp...

Everything else runs fine in the editor, but packaging simply fails. I believe I had this working at one point a few versions back of UE. Is this still possible? If not then how can anyone package a non-source (blueprint only) project? We’ve built some custom plugins with c++, but our main project is just a shell.

Can anyone at Epic respond?