Bug with using track matte in After Effects.

In After Effects, when using a lower layer as a track matte for an upper layer, if the lower layer is also visible, a stray edge (or matte line) will inevitably appear in the composition.

This will significantly cause issues with what I see in the viewport.

he green edge in the image below should not be visible. I suspect this may be caused by sub-pixels of the matte not being fully covered by the upper layer.