I may have partially solved the problem but it gave rise to another issue.
It turns out that I can get the part to render if I increase the radius of the sphere. If it's at the value I want, it doesn't render but if I scale it up by 5 times, then it renders fine. I'm not entirely sure why this is and, ideally, I would like to be able to render it at the original size.
Thanks again for your help.