The Courtship of Wyatt's Father - S6-E16
Continuity mistake: Darklighters are not supposed to die from Darklighter arrows. When Paige and Phoebe get them out of the ghostly plane, a second Darklighter shoots the main one, and he instantly is vanquished. This has never happened to my recollection as DL arrows are meant to only harm Whitelighters or future Whitelighters. (00:35:45)
Plot hole: When Gith takes the potion from Chris, he ends up stomping on it and shattering the potion bottle - making contact with the potion. We've seen that potions don't have to be thrown by someone who's even a witch for them to work (like when Cole's powers were stripped etc) so why on earth would he do this? And how did it not vanquish him? There are other ways he could have gotten rid of the potion that didn't involve a way that really should have vanquished him.
Witchstock - S6-E11
Plot hole: In the opening scene, Chris directs Piper and Phoebe on how to vanquish the amorphous demon. He says that it will attack "fast and hard" as soon as it senses Phoebe's magic when she levitates. But Chris had orbed out of the warehouse and back in, and the demon didn't react to the magic. Later in the episode, it is specifically attracted to a use of orbing, several times.
Witchstock - S6-E11
Continuity mistake: In this episode, it's 1967 and Grams is young and unrecognizable compared to her older self. But in "That 70's Episode," it's 1975 and she looks just like she does today, not to mention that she has two grandchildren. Grams sure ages quickly...
Revealing mistake: Before Jason Dean is shot outside the penthouse, Phoebe is waving her hands trying to convince him that the world is not real and you can already see blood on her fingers.
Witchstock - S6-E11
Plot hole: This episode takes place in 1967, and Penny (Grams) is married to a man named Allen Halliwell who dies in the episode. Allen is supposed to be Penny's "first husband," Patty's father and the Charmed Ones' grandfather. But it was previously established that Patty's father was named Jack, and he died in 1964. Also they hint that Patty is still little but we know she was born in 1950 so she would be 17.
Plot hole: Rick is menacing Phoebe with a gun near the end of the episode. Why doesn't Paige orb the gun away from him? In fact, why did Phoebe make Piper stay upstairs? Piper could have frozen Rick, and Paige could have orbed him back to the prison. There were several obvious ways to resolve this situation that would not have caused Rick's death.
Plot hole: It's shown with the spell that the Halliwells leave for Chris in the attic that if something happens in the past, the future will immediately reflect that change. Chris had changed so much in the past that there should have been at least one thing different that mildly surprised him, even if he was careful to not give too much information to the sisters about the future.
The Power of Three Blondes - S6-E4
Continuity mistake: The Stillman sisters strip the Charmed Ones' powers by using the same spell as Aunt Gail did in Season 2 (How to Make a Quilt out of Americans). But in that episode the Charmed Ones had to first drink a potion and Aunt Gail needed to wait a certain amount of time (at least 30 minutes) before the spell worked. In The Power of Three Blondes, the Charmed Ones never drank a potion and lost their powers before the Stillman sisters even finished the spell.
The Legend of Sleepy Halliwell - S6-E14
Other mistake: In previous episodes it is stated that good witches don't freeze. But after Piper has been decapitated and her head is placed in the manor, one of the students freezes all the kids by tapping into Piper's freezing power. The kids are all good witches so they should not have frozen.
Continuity mistake: Near the beginning when Chris and Phoebe are talking in her office, the loose ends of her scarf switch from being in front of her to being over the back of her shoulders in almost every shot. (00:00:50)
Other mistake: Paige's spell causes Darryl to acquire invulnerability and uncontrollable super strength. When he opens the door of the squad car, he accidentally rips it completely off. When he tries to put the suspect into the back seat, the man flies through the car and barrels out the other side, taking the other door with him. But immediately before this, Darryl high-fives several of his fellow officers, and they are unharmed. They should have been thrown off their feet and suffered multiple fractures in their hands.
The Power of Three Blondes - S6-E4
Continuity mistake: When Phoebe kicks Mabel after the Stillman sisters have taken the Charmed Ones' powers, Jennifer Sky's stunt double's face can be plainly seen, and also her hair is darker and less full.
The Power of Three Blondes - S6-E4
Continuity mistake: During the scene when Paige goes to the citrus plant during the labor rally, her pink blouse is quite short, baring her entire midriff. When the security guard throws Paige out of the plant, Rose McGowan's stunt double is wearing a shirt in the same pink color, but it reaches all the way down to her waistline.
Continuity mistake: When Paige and Phoebe are knocked over by the large monster, the rug moves itself from being spread across the floor to scrunched up under them between shots.
The Power of Three Blondes - S6-E4
Plot hole: Paige sees Margo leading the labor rally at the citrus factory, and then is stopped by a security guard. In the next scene, Margo and her sisters are entering the manor, and then after that Paige is thrown out of the factory. But how did Margo get from the factory to the manor before Paige was thrown out, when she was in the middle of the rally?
The Legend of Sleepy Halliwell - S6-E14
Continuity mistake: When the shaman offers Phoebe the vision quest potion, she alternates back and forth from holding the cup with both hands to one hand. (00:20:15)
Visible crew/equipment: When Phoebe and Paige are trapped against the wall/stairs by the web, the seat that Paige rests on is visible, together with supports under her feet - also note the decorative stair baluster has been removed.
Witchstock - S6-E11
Continuity mistake: Robin falls over backwards after Paige dumps a cannister of marbles onto the floor. But Robin wasn't moving at all when this happened. Trying to walk over marbles will make you fall. Standing still while marbles roll around and bounce off your feet? Not so much.
Continuity mistake: In this episode, Chris thinks back to when he went back to the past. When he and Bianca are on the tour of the manor, there are some costumes that have been worn by the charmed ones. But in the episode "Oh My Goddess (1)" Chris tells Phoebe that Paige died on that day, so how could she have worn something after she died? And if she did die that day, Chris would have never met her, since he was not yet born, and could not have learned to orb from her, as he says in "Spin City." However there are other inconsistencies with that story that Chris mentions later, seeming to suggest he lied about this to get the sisters onside. It may not be a continuity error but as it was never fully addressed in the show just what Chris was lying about (and he obviously told some) we cannot be sure.
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.