Cannot set sliders back to 0 after they have been changed

You can set it to any value other than 0. If you leave it on 0 and don't change it, it works fine. If you change it to some value, then change it to a very small value like 0.1, it works fine. But if you try to change it back to 0, the slider moves (everything on GUI looks normal) but the audio continues to have whatever reverb was there, as if the slider was not set back to 0.