Hey Luos, thanks for the reply. I had a Color Over Life module that I thought might be doing exactly what you said, but even once I got rid of it, still the flicking on and off of some particles, so odd! That’s the only thing I can imagine is controlling alpha or opacity on it.
And thank you for the note about interp modes. I couldn’t see a difference in my case between the auto or auto clamped, but both look better than the linear.