Jason tells Phoebe that it's been 15 months that he didn't know she was a witch. This is impossible as they met 3 weeks after Wyatt was born, and the family celebrates Wyatt's 1st birthday later in the season.
In the season 1 episode "Is There a Woogy in the House?", Piper and Prue illustrate on a map that the location of the manor is at the corner of Turk St. and Laguna St. in the Fillmore district of San Francisco. In this episode, the manor is shown in Presidio Heights, a location far northwest of where the manor was located in season 1.
As Piper is vanquishing the Swarm Demons with her exploding power, you can see a gash on her forehead. Then Phoebe and Paige orb in and take her back home. As they orb in, the gash on her forehead is gone. But Leo comes over and heals the gash later.
Richard's brother Steve no longer has the scars on his face and neck that came from their family war with the Callaways, as seen in season 6 episode 5, "Love's a Witch".
Around 19 minutes in, when Paige and Piper go back into the demon catacombs they look down and see they've been going in circles due to their footprints are visible in the dirt ahead of them. When they hear the demons coming and the camera pans away from them in the direction of where the demon footsteps can be heard, the ground is made of stone - not dirt. You continue to see, and even hear, the stone floor as the demons walk by them; and again when they come out of their hiding spot - which shows the ground behind them, which is where they first walked in. So stone all around! NOT dirt.
Phoebe is tossing French phrases about when she receives Mata Hari's karma, but when Jason is about to be killed she says "Goodbye, mi amor," which is Spanish. The correct phrase should be "Goodbye, mon amour".