orangestar Thank you for sending your skeleton data files! I have confirmed that the blend mode of the slot (tx_light2) where the problem occurs is is set to Additive instead of Normal.
When a slot uses additive blending, its attachment is rendered additively if the image has a background color. If the background is transparent, the attachment is rendered additively if it is on top of other images, but it is not rendered additively if it is on top of the transparent background. If the attachment image uses opaque black, you will see the black where it is on top of the transparent background.
Looking at your code, you've made the background of the player transparent, which is why the black background of the vfx image is showing up.
I think the solution to this problem should be to make the background of the original texture used transparent instead of black, or to make the background non-transparent.
