Here's what one of the site modifiers looks like when I select "show 3d".   Half of it sits on the surface of the model, and half of it seems to be at zero elevation. I don't understand how it's ended up like this. I don't know if it matters, but I suspect it does and is linked to the problems. I don't know if there's any way of fixing it other than tracing over it with a new modifier, and then deleting it.   The effect of this modifier is as it should be, when I look at the