hey,
there is annoying bug with UEF SCU shield when they build: You can't build anything if you order to build something with two or more SCU shield selected, they begin the building but stop directly after that and then the building die by itself. To build you need to select only one and then assist with other.
This bug is older than the last patch but i didn't see anyone posted it on the forum (or the post is really old ...) so here i am.