Each sale and purchase depend on the next one proceeding smoothly so if one part of the chain falls through, it can have a knock-on effect for everyone involved.
A chain can break for various reasons. For example, a buyer might pull out due to a change in circumstances, a mortgage offer could be declined or withdrawn, or a survey may uncover serious issues. When this happens, all the linked transactions above and below the break can be delayed or abort. This can be incredibly frustrating — especially if you’ve already invested time and money into conveyancing, surveys, and mortgage arrangements.