Has anyone experienced a significant drop off or increase in volume when using this pedal? In other words, the pedal seems to be really sensitive to any change in how much force I use to pluck/pull the string...a whole lot more sensitive than when I just usie my amp. A slight reduction the amount of finger pressure on the string results in the volume dropping off the map...almost not being heard. Conversely, a slight increase in finger pressure results in a major increase in output. I'm using the factory settings/patches.

Most patches have a noise gate applied, you might be sitting right on the knee of the trigger. Try increasing the input gain to overcome this. Or, make your own patches. Zoom are known to create over-processed factory patches.

I haven't had that problem with mine. I would think it could only be the patches you're using. I never really tried the factory settings but rolled my own.
Maybe try tweaking the compressor or noise gate or something.

Yeah, what they said. And make sure noise gate is not on 9.
Tweak, and your problems will be solved.