In the final scene when the Sliders are supposed to be on a world of nudists, you can clearly see through the screen door the lady is wearing bra and panties.
In Season 2, Episode 3, "Gillian of the Spirits", Quinn and his clothing is ephemeral and unable to touch physical objects, but in one scene he's sitting on a chair and with his jacket draped over the back.
Quinn slides at the beginning wearing a yellow raincoat. On the next world, he realizes he's invisible and can't physically interact with anything. Eventually, he discards the raincoat and starts wearing a dark jacket. This jacket was not on his person before, so it's impossible for him to start wearing it.
While Michael Mallory is holding a gun on Arturo, the Professor explains that the slide portal will be open for 60 seconds and then close on its own. The portal actually stays open for 2:47, and more than 55 seconds have already elapsed by the time Arturo says that there are only 45 seconds left.
At the end of the episode, Arturo says there's seventeen seconds until they have to slide, but about twenty-seven seconds elapse before he activates the timer.