Gcode Anomaly - holes/divots

I ran across this issue with Slic3r and thought I would share my findings in case anyone else runs across this.

I have a model that has a divot modeled in that sometimes slices correctly and sometimes Slic3r covers with filament for no discernible reason. On the left side you can see the divot where I had even made into a hole drilled through the other side is covered over. On the right is what the Gcode should look like.

What I did to solve this is simply rotate the model 180° with ReplicatorG. This is stupid and shouldn't make a difference but it does. I don't have time to delve into the why this happens but for now there is a solution beyond reworking one's model.