Bug: Arch in hammer is hollow

[QuadrupleAndy]

Describe the bug

Sometimes when using the arch block tool sides appear to be invisible. No idea if the map compiles with it or not, because I couldn't reproduce it again.

Issue Map

I couldn't reproduce it no matter how much I've tried to do so.

To Reproduce

1. Open hammer
2. Create a new brush with an arch tool
3. See (or not) that sides of the newly created arch are transparent

Operating System

No response

[Halo3Rodent]

Issue only happens when creating an arch brush in the side (x/z) view in Hammer, does not appear to happen when creating an arch brush in any other view.