When using larger extrusion widths (eg 0.75mm) infill (eg 10%) can end up producing quite large gaps (eg hexagonal infill).
I normally print solid infill (0.2mm layer height, 5 top layers) quite fast (100mm/s) and normally that works fine. However in the above case the first layer of solid infill is going to be quite messy as extrusions tear in the gaps between infill structures on the faster (i.e. longer) runs. To create a blanket reduction in solid infill speed can have too higher cost in part time. However the problem would easily resolve itself if S3d could recognise that, in certain circumstances (gap >= bridging distance) the first layer of solid infill should be categorised as "bridging" and the "bridging speed" applied.