Hello, I am having the exact same problem and I am using version 3.0.4
I want to use a “modal box” button to open a vimeo video as a pop up and is not working.
I noticed that the only button that works when I have the galaxy particles is the “advanced button” which is maybe what you are using on the demo, but this option does not support pop up.
The modal box works fine as long as is not part of the galaxy particles. So, this issue must be only when working along the particles.