Hello all,
Looks like the thread has been idle for a while.
I have good news! I have managed to merge the barrack model within blender and redo the UV mapping. Now Unreal shows only 1 element. So no more issues with 7 elements.
Also I have done the 4 stages of construction for the Barrack model and made sure they all share the same UV layout.
When you have resolved the issues with Git, I will push it there.