Unwanted gap around blurred objects touching screen edges

When I render a scene that has a Blurred and Toned object, it creates a visible clear gap around the screen borders where those objects touch the edge. When I disable the Blur, the clear border disappears. I’ve attached images to demonstrate, with Blur ON and OFF. Observe the two objects in the lower left and right corner of the screen.

Any idea why this happens? Is it a known bug, or a feature I’m using incorrectly?

Not sure why this is happening ?
Works perfectly here, without any visible gaps.
If you like, here is my setup:


I should have specified that I am using Toon Boom Animate 3.

My hierarchy of layers is like this:


  • Symbol
    – Tone
    — Drawing

If you insert a directional blur with an angle of 45 degrees between the blur and tone, you can probably correct the effect.