Line coming out of 3D inflated object

Hi there! I've inflated an object and it has this weird line going down the side of it which goes beyond the artboards, and I can't select it/get rid of it.

It seems to disappear when I turn off 'shadows', but then it messes up the lighting effect I took so long to get to a place I was happy with, and can't get it right again.

Does anyone know why this line appears, and/or how to get rid of it?

Thanks in advance!