Gillian Of The Spirits - S2-E3
Plot hole: Quinn is unable to touch anything or anyone, yet he is somehow able to sit in a taxi cab. Why doesn't he fall through the car seat?
Suggested correction: This is a common trope with ghosts or people on the astral plane or out of phase. It's not a mistake since it's not a real life thing and it's not explained how it works (although there are some theoretical physics theories behind it). He can sit in the cab the same way he can walk on the ground and up stairs.
Post Traumatic Slide Syndrome - S2-E8
Plot hole: Since Quinn's double built a sliding system in his basement, our sliders could have used it to reset the timer and go home, just like they intended to do in the episode "Eggheads."