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...
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.
Witchstock - S6-E11
Continuity mistake: When Chris orbs Phoebe from Hong Kong, Phoebe raises her arms to hug Piper twice. (00:00:50)
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.