Continuity mistake: In a matter of 15 seconds between David's ship exiting the hangar and shooting 20 miles upwards into space, shadows on the ground indicate very different positions of the sun. (00:51:05)
Continuity mistake: When Carolyn first enters David's room at NASA headquarters, she introduces R.A.L.F. Between shots, David wraps both arms around his knees. (00:30:35)
Continuity mistake: When David and Max are lost and in need of directions, they spot a red Mustang cruising along. The Mustang is within throwing distance of a T junction at first, but then in the following shot it's suddenly about a quarter mile away from it. (01:09:30)
Answer: Carolyn wouldn't have wanted David anywhere near the UFO as it could've been dangerous, so it's safe to assume that "Max" programmed the R.A.L.F robot. Although Carolyn didn't have anything to do with with David's escape, it wouldn't have escaped unnoticed that the R.A.L.F robot was in the hanger where the UFO was. Given that she's always the one with the R.A.L.F. robot, it's safe to assume she was acting worried that she'd be blamed rather than acting "shifty"