Synfig Animation Studio

I've discovered how Straight Onto doesn't do its work properly for non
tiled renders.

Download the attached file.
Open it and set the time to 16 seconds. Now zoom in and out and see how the
mouth of the character changes.

The mouth ("boca") is composited by this:

Inline Paste canvas ("boca")
-Inline paste canvas ("lengua")
--Inline paste canvas ("lengua") -> Straight Onto
---Some layers to perform the tonge
--Region layer (wide open mouth)
-Region layer ("boca")

At frame 16s the "lengua" (Straight Onto) layer is moved apart of the wide
open mouth region layer. So the "lengua" and the wide open mouth layer
wouldn't be shown.
But notice that if you render the scene at that frame (exactly any frame
after frame 15s) it renders the wide open mouth although it wouldn't be
shown because the Straight Onto paste canvas layer is far away.

On the other hand it renders OK (mostly) if the tile render is used.


NOTE: the file looks for a image file called paper.png that is not
included. It doesn't affect to the problem.