The point of DSP+FX is that when you deactivate the pedal/effect, the trails from the Reverb or Delay are still present, instead of suddenly cutting off. That way you can enable huge reverb, set up some sort of strike effect/drone background, and then disable it and play over it. Or something like that.

If you don’t need that just put it into Bypass if you so desire. Or regular DSP. That way the reverb will be cut off completely as soon as you deactivate the pedal.