This is totally a Jitter specific issue. I’ve opened a Q/A on their forum. Stay tuned for a reply from Cycling. From now, this is near as I can tell, a Jitter specific issue. They are not clearing the same way as most other GL apps. Its not a “wrong” thing to do, but a choice (how the trails happen). Now, you could probably fiddle with the blend mode to get something appropriate, but not having GL_COLOR_BUFFER_BIT cleared when erase color is transparent black is going to cause compositing issues regardless.