Before it prints, not that I can see. I cannot figure out how to make what is on the print bed more visible - less translucent.

After, or while it is printing, it does show the filament being laid down for what actually was printed.

I am making a prototype part. it printed a face that is not, and was never on, the file. Here is the workflow:

1. designed in sketchup
2. exported as 3D Model (.stl file)
3. imported into matter control

On the first print, I could see that has generated supports that I didn't think should be there. . so I stopped the print halfway through, closed and rebooted everything, and then imported the file again. When I started the print again, I paid attention to both the supports that I could see on the matter control screen and on the print bed, and it all looked good. When it got to the point that the "unneeded" supports would be printing, they were not printing. I tried playing around in Matter Control with the view, and could not see supports or anything that looked wrong on the print bed view. So I thought all was good. When i got back to work this morning, I found an extra face on the part that really makes no sense; its not even like it was there once and got deleted. I can see why the supports were generated the first print- to support this face. but then why were they not generated the second time, and it still printed the face?

Where do I start in trying to fix this? I think I could start over and draw it in SU pretty fast this time, but i really want to know what happened and how to keep it from happening again. Pics below.

model 1
print 1
model 2
print 2
model 3
print 3