The "paste into background - not an obstacle" function does not seem to work correctly with any object using physics based movement.
Not sure if this is a bug or something I'm missing in the physics engine object properties.

I've attached an example - example.mfa

pressing space bar fires a bullet that destroys backdrop on impact by pasting a circle into background as "not an obstacle".
Pressing V creates an "antibullet" that creates obstacle instead by pasting into background as obstacle.

The player character with physics-platform movement will collide with newly created obstacles correctly, BUT doesn't seem to respect any newly created "not an obstacle" areas and will still collide and be stopped by the original obstacle shape (even new ones created with V then destroyed).

This behaviour happens with all physics based movement options, but not the various non-physics movement.

So am I doing something wrong?, or is this just something that physics movements are not suitable for?