My Car is Making a “Clanky” noise

I worked at a GM Dealership and did a PDI and on the roadtest heard a rattle in one of the doors. Took the panel off and found an am/fm cassette shoved in the door. The car only had a an am radio in it. Probably it was a car being built for an employee of GM. and it was watched going down the line. So I put the radio under my bench and sent it on it's way