that is hard.......try the UESP for answers, it has a solution to that
"The Left switch opens the front door and the Right switch opens the back door, however you cannot operate both at once. The trick here is to flip the Right switch to open the back door when the machine starts making noises and the tubes overhead move. This will open the inner door and the outer door will open automatically to release the Fabricant"
that is what it has to say on the matter, try it out, it helped me.