Our stroller seems to have locked down one side and it won't fold.
Hi, Beety,
You will definitely need to contact the Baby Jogger customer service, or the seller/distributor you got the stroller at/or any around you, as there is probably damage in the joint/internal wires, preventing the folding down. It is not a thing I can help you with long-distance, definitely you will need servicing.
Your -very berry- Eli.