***Stuck in hangar possible workaround***
I get this alot, and its always once i finally afford an Atlas. What usually works for me is walk to the invisible wall at the opening, and then eject, or powerdown and leave. Doing this causes the mech to move its legs in such a way that it will usually "force" a leg over the clipping error, and then when you get in the mech and power up, it drags the other leg over it as well, allowing you to move. This works about...90% of the time for me. Sometimes i have to be moving when i eject, sometimes i have to be standing still. If worse comes to worse, just start buying hovercraft.