Taz 6 Dual Extruder V3 Cura slicing Issue

I have a Taz 6 with a Dual Extruder that works great except that when I slice the models using Cura, an artifact appears on the grid (and ends up printing) that is not at all part of any of the layers. It only appears on the grid when I select 2 different hot ends for parts of the print. It still aligns perfectly, it just has this strange artifact that is a square on the upper right hand of the grid. Anyone seen this before?

I think that is some sort of purge block when the print switches print heads.

That would make sense, except that it is the first thing to print… Very odd. Seems to happen every time I change the extrusion head. If I use the same head for both models, no issue. It also draws the light gray bounding box on the left of the Grid. I am sure there is something I am missing with my configuration. The good news is that the print still seems to work!

Yes, the grey box represents the pillar it will print as it prints your model. The purpose of that pillar is so that whenever there’s an extruder change, the printer has a place to prime the new extruder and safely deposit the material (rather than doing so on your model, where it might result in gaps if the prime was slightly under “perfect” or blobs if it was slightly over “perfect”).

If you print with only one extruder, there’s no need for that pillar – so if Cura is smart enough to drop that pillar in that case, that’s an excellent optimization.

That’s the prime tower. Capture