Plot hole: In the episode where the Sliders go to the world where Quinn sees himself as a child attending his father's funeral. Quinn helps his young self deal with bullies. Quinn repeatedly mentions is was all happening the way it did on Earth Prime. The flaw here is that in the Series Premier episode, they showed a picture of Quinn, his mom and dad. Quinn was a teenager in that picture, not a kid. Therefore the events in the alternate world they were visiting could not be happening the exact same way. The man in the picture is the same man shown as his father in the other worlds so it cannot be a "stepfather" that his mom remarried.
Plot hole: The length of time the vortex stays open varies throughout the show and seems based on when the writers want it to close. In several episodes the vortex is said to stay open for 60 seconds. Sometimes the group go through immediately (to avoid danger) and sometimes wait (to say good-bye). Yet it will still close after the last Slider goes through, even if it's open for less than 15 seconds. And it's not closing because the 4th person went through since sometimes more than 4 people go through.
Character mistake: The Sliders are constantly trying to interact with a new world despite not knowing anything about it. This action often leads to misunderstandings, arrests, or threat of death. Sometimes there's even posted signs that they don't bother reading until it's pointed out by someone they've upset or annoyed. Yet they continue this action. They played a death lottery without asking question, order beer when it's not available to them, or try to pay without local currency.
Chosen answer: Remember at first Quinn's timer is working perfectly (it's only because they slide off the ice age world early that it begins to malfunction) & given Quinn's intellect he would have devised a way that he could open a wormhole near him so he wouldn't be trapped on that world for 29 years.