Since no one else replied:-
I haven't seen this issue but have had some models sliced and noticed some gaps. I was slicing from Repetier and noticed in the communication box at the bottom there were error messages being reported from Slicer.
I changed a few dimension on the model and it was OK.
I suspect that there are occasions where dimensions dont add up for Slicer. Im talking fractions of mm.
I don't know enough about the models and the Slicing process to explain it but if you think of all the steps in translating some CAD indtruction into Gcode I can imagine that numbers being rounded up or down through several steps could lead to the occasional problem. Particularly on curved surfaces.
Its a bit like printing thin walls where you want the wall to be a multiple of the extruded width.
I would monitor the Slicer reports and try changing some dimensions slightly.
