Maya states that she is the last living Psychon, but Dorzak (1977) featured another surviving member of her race, Dorzak, who was a prisoner of the Crotons.
When Koenig removes the wire gauze and clambers into the shaft, the "solid" wall wobbles as he does so.
While Alan Carter - no slouch in hand-to-hand combat - had failed to affect a Dorcon guard whatsoever with several punches, Commander Koenig mysteriously knocks out a guard or two aboard the alien ship with a single punch.
In the epilogue, Tony informs the Commander (who had only been away from the base for a few hours at the most) that the damage repairs are well in hand. That short amount of time probably wouldn't even be enough to assess all of the damage.