Yeah, has to be the light motor.

If it fell off I'd just leave it off. Worst case you'll get some dust in there over a LONG period of time. I've had my Getaway for over 20 years and my cover fell off some time ago. If it hasn't been played in a long time I get a little motor hesitation for a few seconds (lights up but won't move) then it starts running and you are good to go.

As for objects falling on glass, I'd be more worried about the cover hitting the glass for the translite. Impact on the edge could cause a glass shatter and you now have a damaged translite. I've had plenty of things fall on top of playfield glass and nothing happened. I've knocked playfield glass over on cement and nothing happened. Other times you look at glass the wrong way and it shatters. You never know....