I've discovered my crashes are being caused when using the vertex maps. I ticked the 'speed' map so I could have different refraction colours for different areas of the mesh, which looked great as a still but would crash on random frames through picture viewer/render queue on both the Mac and PCs.
Hard to know if this would still occur if the meshes were made editable without somehow baking every frame, so it would still be useful if someone know's how to do that?