Do you know anything about the history of the house? Or perhaps any oddities in your family history? It's possible that whatever is going on with the model is relatively benign and your parents simply didn't want you to get freaked out by/risk damaging the model, but where there were noises you heard also it seems like there's more to be uncovered. It might be worth confronting your parents at some point, but it would probably be better to covertly gather info before then. Or it might just be safest to try and forget about it, avoid the basement, and move as far away from the house as possible as soon as you get the chance