While Dr Smith is lying down on the table with the large blade swinging back & forth and the Thief looking on, the swinging blade disappears and reappears between shots.
When Will is forced to go to work by the slave, he peddles backwards the second time around.
Unlike Earth type planets, asteroids do not have a breathable oxygen atmosphere. Will and the others would not be able to breathe when visiting the Thief.
When Will enters the sedan chair, and the door closes, he puts his hand through the window, meaning that there is no glass. At that point the sedan takes off into space and heads for the asteroid. Facing bitter cold, no oxygen, and the inside of the sedan being unsealed, Will wouldn't live more than a few seconds.