The front bumper of the car was undamaged, even though it appeared to have hit the boulder at considerable speed.
When outside the house, Andy Thorne shines his torch/flashlight on Lamont, who is up a ladder to the barn. A bright light moves from left to right that is obviously not the light from the torch/flashlight but probably a spotlight operated by the lighting crew. When Andy lowers his torch/flashlight, the movement of the light on Lamont doesn't match his movement.
Around 33 minutes, the ghost image of a crew member can be seen walking around where the boulders are coming down the embankment from.
After the lights come back on the telephone rings and the wife answers the call presumably from the phone company. She says yes the phone has been out of order and that everything is all right now. She acts as if she is the homeowner and doesn't mention that the actual homeowner is dead nor does she ask for help or call the police herself to report the death.
Unlike the tumbleweeds and rocks, the frogs didn't actually do any harm to the people, just threw themselves at the people and bounced off. Other than being strange and scary, they seem harmless and do no damage. The characters could have used that opportunity to escape.