Are you planing on making the launch vehicles for the mission? And there is a bug when some parts deploy when they are brought into the VAB. (The Explorer Comm Sat deploys its solar panels in the VAB and cannot be closed. This is one example to help you )
Ignore the bug. Its probably conflicting with other mods. I'll uninstall them and see if it works.
It now works fine. I also installed the Firespitter plugin. Why does the game lag when the HLV Landing Frame in put into the VAB, but then its fine when I retract the landing legs?
