Continuity mistake: When Jackie leaves the office, the clock reads 10:12. The ensuing continuous scene with Winter and Mr. Smith is almost 6 1/2 minutes long, yet at its end, the same clock has advanced only 2 minutes, now reading 10:14. (00:33:00 - 00:39:15)
Continuity mistake: When Mr. Ferguson is measuring the wax figures, he's shown holding a tape measure up against the figure of Landru (the one holding the rope). In the next shot, the figure is shown with no one near it. The next shot again shows Mr. Ferguson measuring the figure. (00:45:35)
Passage on the Lady Anne - S4-E17
Continuity mistake: During their conversation over tea, Mr. McKenzie tells the Ransomes about the other people aboard ship. One elderly couple, the Whiteaways, are sitting in the background in almost complete shadow - until McKenzie introduces them. Then we see them in sudden brilliant light, and they've shifted their seating positions relative to the table. When we cut back to the master shot, they're back in shadow and back in their original positions. (00:29:55)
Continuity mistake: As Ilse walks toward the front of the classroom, she passes the kids in the last row and is even with the kids in the next-to-last row, but in the following shot, shown from her point of view, she's passing the kids in the last row again. (00:30:45)
Answer: It's explained in the episode. The aliens are experimenting to see how humans react to various scenarios. This just happens to involve them using super strength.
Thanks. It's been a long time since I saw the episode so I forgot.