This “bridging” happens when the extruded string does not contact/bond to the layer below it and then it’s over… the head still makes the circular path but the extruded material just makes a straight line…
And it seems that the trigger for “contact loss” in this particular case is the toolpath change when the round indent starts (or an error in the STL that Netfabb cant’t find).
My guess is the z-code check is just a way to verify it’s valid z-code, not that that z-code created is a well formed object. The check in Z-Suite does that (usually). I ran this file through netfabb and it didn’t make it any better. So my guess is this stl is fine and should be one to send to the Z-guys for future improvements to the slicer.
I have printed the Dandelion vase successfully sort of. I scaled it to 50% and it’s bottom came off with the raft. It did have a lot of lines at various layers but it printed, and the lines were all the way around. I guess those empty layers could cause the issue you had.
I made my own version based on the Dandelion vase but with a slightly different shape and 2.5 mm walls and a 5 mm base. My thoughts were it might be more water tight it had a thicker base. It just finished printing. I used 60% fan and got a lot of stringing inside and it is rougher on the opposite side of the fan too. Otherwise it turned out quite nice. Too bad I can’t get inside to clean the stringing.
I think part of the problem is the shelled version wall thickness is only .5mm to begin with. Then you scale it down to 70% and wall thickness is now .35mm. Just a guess on my part. I’m thinking Z-suite has a problem calculating something smaller than the nozzle… At 94% tool path looks fine in Z-suite. (but it is still single wall)