Why is Cinema 4D sculpting only on the back of my object?

I'm stumped as to why Cinema 4D is only letting me sculpt on the back of my object. This sounds like a problem with my normals however they are all aligned and I have already tried reversing them. I'm able to sculpt just fine from behind, but it is unproductively counter-intuitive.

Is there a checkbox I hit by accident?

Using R15 on Mac.