Visible crew/equipment: Right after the phone conversation, everybody starts going towards the door. As they do, if you look at the couch on left you can very briefly see a shadow of something moving across it. It couldn't be any of the actors since they were all either outside or on the other side of couch.
The Mind and the Matter - S2-E27
Visible crew/equipment: While Beechcroft talks to his boss in the men's room, the boom shadow moves across the wall at the upper right of the screen. (00:03:35)
Visible crew/equipment: When Chris escorts Grandma Bayles up the stairs, a blocking mark is plainly visible at the lower right, chalked on the carpet. (00:05:25)
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.