Well, don't you just love this.
We changed the thickness of a sheet metal part that was designed in 1.5 to 1.2 thick, and radius on the outside corner migrated onto another position on the part, only on the flat pattern.
So there is a drawing conflict.
But the supplier used the flat to cut a load of scrap before anyone noticed.
on the new thickness part, delete the flat from the drawing and the config on the part, and re-insert the flat and all is correct.
Meddle with the thickness and the issue comes back.
2016 files attached, see for yourself, it reproduces. This was 2016 sp5, I wonder if it does it in 2017?
I haven't tried creating a new part to see if it does it again.
I've reported it to my VAR.