Find the room filled with lots of boxes. Do not destroy any boxes with red triangles or any boxes on top of red triangle boxes (the top box destroys the one under it, etc.). The right arm part MWG-GS/80 can now be found on the ground. Use your map near the first target to find a secret passage behind the wall. Destroy that part of the wall and follow the secret passage until you reach a room with one box. Destroy the box to find the head part MHD-MX/BEE