I'm experiencing a fill issue where there are voids/gaps in areas that seem to be wider than 2 passes of filament but not quite wide enough for 3 passes. See the image to see what I mean.

Is there a way around this? Currently slicing at .1mm, going to .05mm or .2mm doesn't affect the fill. I'd like to fill up these areas as much as possible without affecting the rest of the print. Any ideas to help me out?

Do you have the .stl file? I want to slice it.

Maybe tweaking the smooth option and the Grid parameter in the Fill options can avoid these gaps.