Symmetry with a directional brush?

Hi! I’m new to ArmorPaint. I’m trying to create a brush with “directional” enabled, but this seems to be doing something odd to the “paint with symmetry” tool. With it enabled, instead of painting symmetrically, it will only paint the opposite side of whatever I try to, leaving the side I actually painted completely blank. Which is kind of useless.

Is this normal, or is it a bug? How do I fix this?