Carpe Demon - S7-E14
Revealing mistake: After Leo's meeting on the bridge with two of the Elders, it cuts to Phoebe walking down the stairs as she catches Drake dancing, and when he approaches Phoebe to take her hands, the top of the set with lighting can be seen in the dining room.
Carpe Demon - S7-E14
Revealing mistake: When Miss Donovan is chained up, it is very obvious that her hands can easily slip through the shackles.
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.