Desperate Housewitches - S8-E4
Continuity mistake: Paige asks how The Source was previously vanquished, but she was there both times: when the original Source was vanquished, and again when they vanquished Cole. Also Phoebe wasn't actually there for the final vanquish of Cole, but was taken back by Cupid as if it was her memory.
Continuity mistake: After the opening credits, while Piper tries to persuade Paige to help with the speed dating at P3, in two shots facing the bed and in the shot facing the mirror showing the "Jaime and Jo Bennett" reflection, the lamp on the far side of the bed is turned on. When Leo is holding Chris he walks past the mirror, and in this reflection that lamp on the far side of the bed is turned off, but in the next shot facing the bed that lamp is on again. (00:04:55)
Continuity mistake: After Antosis and the Imp Master are vanquished, in a following shot we see Phoebe wearing a robe and sitting on the bed, then we see her "Julie Bennett" reflection in the mirror, but notice that even though the style of the robe is the same, the colorful designs are quite different in the reflection. This happens again later when the sisters and Leo are seen in the mirror's reflection, as they undo the spell to reveal their true selves. (00:33:25)
Continuity mistake: When Paige and the reporters interrupt Piper and Leo's argument, Piper's arms move from out in front of her to her sides. (00:32:55)
Continuity mistake: When Paige goes to talk to Henry at the police station, her arms are on her hips in the shot from the front, but down by her sides in the shot from the back. (00:14:20)
Continuity mistake: When Paige arrives back at the manor after being stood up by Henry, Piper has both her arms on the table in front of her. Her arms are then crossed over her chest, then back on the table. (00:16:30)
Continuity mistake: Season 8, Episode 14, "12 Angry Zen": When Phoebe finds Paige at the manor after the demon/Zodiac fight, Paige rubs her neck with her left hand. In the next shot, it's suddenly her right hand on her neck. (00:28:55)
Continuity mistake: Episode 8x17, "Generation Hex": When Phoebe hands Paige her wedding gift, the way Paige holds it changes between shots. (00:01:20)
Continuity mistake: When Candor interrupts the Noxon demons torturing a student at Magic School, Rondok turns around to look at him. In the following shot, he's facing the other way and turns around again. (00:06:10)
Continuity mistake: When Phoebe and Cupid visit the memory of Phoebe revealing she is a witch to Dex, past-Phoebe has her hands down by her sides, but then her left hand suddenly jumps to her purse strap. Not only that, but in the original episode ("Rewitched"), Phoebe's hand remained on her purse strap the entire time. (00:11:05)
Gone With The Witches - S8-E20
Continuity mistake: When the leprechauns are called back to the manor from Magic School, O'Brien cradles his injured arm in his left hand. In the next shot, his arm is down by his side and he moves it to his arm again. (00:25:10)
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.