Project DLL Version Error When Moving to Another Computer

Hi,
Our workgroup is running the same custom build of 4.19. We had no problem sharing the project until we added some bits of C++ to the project. We have no problem rebuilding the project in Visual Studio. The problem is that when we try to open the same rebuilt project on another workstation, we get the dreaded project DLL built with a different version of the engine error.
Why would UE think that two copies of the same engine (less intermediate and cache files) are different versions when opening a project?
Thanks!
-Donald