During the Hungry Brain sequence, the jazz band's trumpet player is shown playing with his horn "open" (unmuted), but the trumpeter heard on the soundtrack is using a mute.
At about 1:18:50, Kreton runs into the barn and slams the doors shut. Conrad is shut outside and banging on the right-hand door. Kreton is inside and trying to close same door, but it hasn't latched yet, and for some reason Conrad can't push it open although there is nothing stopping him.
In the opening scene, Mr. Delton, who is the leader of a highly advanced planet, turns off his video screen by clicking a common electrical switch.
Kreton is protected by a force field/shield to keep people from touching his person yet at the Hungry Brain patrons and staff seem to have no trouble touching him.