Womb Raider - S4-E21
Visible crew/equipment: While Piper, Phoebe, and Paige are in the magical cage, the Dark Priest, the demons, and the Seer are all killed/vanquished, then when Piper kicks open the cage the sisters walk out, and we can see the black mic transmitter attached to Phoebe's waist, at her back on the right. (00:38:40)
Womb Raider - S4-E21
Other mistake: Piper tells Page that her doctor told her she probably wouldn't be able to conceive because of scar tissue from blunt force trauma. But Leo has healed Piper, if there was scar tissue after Leo heals, then all 3 girls should be covered in scars.
Suggested correction: They are thrown around quite a bit before even finding out Leo is a whitelighter. Also, he doesn't heal them every time they get thrown or hit in the abdomen. In fact, we usually don't see him heal them at all if they're just thrown across the room or punched in the gut, unless there's a visible wound.
Womb Raider - S4-E21
Continuity mistake: When Phoebe gets a stomach cramp in Detective Miles' office, she doubles over in pain. In the next shot, she's standing up straighter than she was. Her right hand also moves from the chair in front of her to her stomach. (00:22:55)
Womb Raider - S4-E21
Continuity mistake: When Phoebe talks to Morris in Detective Miles' office, her hands change position instantly between shots. (00:22:45)