Hi Gavin

Thanks for posting in the community.

When working with Swimlanes it's important to note that what causes all of the shapes within them move together is them being “magnetized”. Swimlanes are automatically magnetized when added to a diagram but it is possible that it has been disabled on your swimlane. You can turn magnetization on/off this by selecting the swimlane and clicking the magnet symbol on the top-right edge of the editor.

Hope this helps!