Given the length of time it would have taken a flight to Uranus to occur, let alone the time it would have taken once the crew is "frozen" by the alien for the apple to have shriveled to that degree, the crew members would have had substantial beard growth.
The spider attack used footage borrowed from The Spider (1958), and is in black and white. As such, the spider attack scene goes back and forth between black and white and color.
When the crew opens the door to the barn, a piece of equipment is swinging. It then stops swinging, but when they enter the barn, the piece of equipment is still swinging.
The full size alien model has one large eye with an eyelid that dramatically opens and closes. The miniature version has one snake-like eye.
There are several factual mistakes, such as the clouds and sky color as the ship lands on Uranus, the solidity of the surface (which is actually gaseous) and the gravity, which the crew reads as 1.05 Earth gravity when it is really about .9 Earth gravity. Of course, this could be explained as the power of the alien brain on Uranus affecting all these factors.
Concerning the astronauts' rubber suits, oxygen is not really an issue as their faces aren't fully covered by the glass welder-style visors.
At the end of the story, there's a scene where three characters are still in their space suits in the Earth-like woods. When one character falls, you can clearly see white clothing through a long vertical slit in the seat of his blue space suit.
When the men run out of the frozen cavern, a stalagmite wiggles as they pass.
Overhead shots of the rocket interior reveal the studio's wooden plank floor.
When the astronauts enter the cave for the second time, Eric has red or pink paint on his legs, when disappears several shots later.
When near the alien brain, Commander Eric observes that the pulsations in light match the pulsations in radiation seen on the detector but the frequency of the two events are clearly not the same (the light changes are much slower).