skyhawk03e
commented
3 years ago 
I have exactly the same problem! Perfect STLs (three layers, only three splices), and when sliced in Canvas, there are what appear to be multiple, random bit of extruded filament (to be extruded, as I've never gone ahead with any of the prints that have this issue, and there are many), usually in mid-air, as you've discovered. These 'items' don't appear if sliced by any of the other slicers I have, and I've also verified that I can change the slicing behavior of Canvas, but importing only the top, middle or bottom layers of this very simple print, and slicing only one layer at a time. Different 'sprites' appear. Definitely a bug in Canvas slicer.
I have made a Ashtray and after slicing there are lines of infill that should not be there at the top. When it gets to the top of the ashtray Canvas has decided to head into the middle in the air in 4 or 5 locations and draw infill lines into the center in air. I am happy to have someone contact me that can see the Canvas3d.io model. I see no way to control this and no changes to make. This model prints and slices fine in Prusa and prints on an Ender.