discovered the following bug:
1)Apply WebGL effect on the sprite
3)Put many instances of this sprite on the canvas
2)Than disable WebGL effect in the event editor for all the sprites
3)Pick one sprite and enable the effect for this particular sprite
--> Bug: WebGL effect is enabled for all instances.
Something similar happens inside a family, with different sprite objects - WebGL effect is enabled for all instances of the same sprite type. Here's demo capx: