Kay, the Singer 237 is a great machine. It is one of the last all-metal interior machines that Singer made. It is reliable, heavy, and sturdy, and has a 1 amp motor, making it more powerful than a 15-91 or 201-2. There's only one piece of plastic in the interior, and that's the little gate that holds the bobbin case in. It's possible that some people are confusing this with a different machine.
Noises by themselves are nothing to be scared of, nor is a jammed machine--sometimes it's as simple as a thread tangle blocking up the works. It would be a shame to pass on a quality machine like a 237 if it is something simple, but because I don't have a clear idea of what the noise sounded like, I can't begin to guess what it might be.
Do you have a mechnically-inclined friend who can come with you to check the machine out?