What a revelation..I think I've finally cracked it just now and that is - TURN OFF COASTING ! ... I just tried that and the pre-vis of the print is flawless. - No blips in the outer shells at all....
The visualisation actually shows where coasting takes effect....by there being what looks like a gap in the printing, which is actually what is happening! And your printer magically makes up for this "gap" by a process called over-extrusion....which it does naturally.
Turning coasting off is likely to cause zits......which is the unwanted over-extrusion.
