Repo Manor - S8-E13
Other mistake: When Piper blows up the dollhouse, killing Pilar, Phoenix and Patra, you can hear the sound effect of telekinesis, despite Piper's power being molecular combustion.
Charmed (1998)
1 mistake in Repo Manor - chronological order
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Trivia: Holly Marie Combs's real life pregnancy with her son Finley Arthur Donoho was mirrored by Piper's pregnancy with Chris in this season.
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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.