Response from LEGO SHOP
September 5, 2019
Marine, Customer ServiceOh no, we're sorry to hear that one cart flew off, I hope all of your minifigures are okay! To prevent any other incident, please make sure that the little wheels underneath the cart are in place fully clicked in. Our age recommendation for this set is 16+, depending on your children's experience they might need more or less help to build. For the chain, you'll need exactly 203 links (we always give you some extra) and make sure they are fully clicked with one another as well. Our expert should be in touch with you any time now if it's not done already. If you need more help, feel free to get in touch with us by phone, chat or email via LEGO.build/Service.