I believe the same thing happens when exporting from maps.arcgis.com/apps/webappviewer.
Turning on/off locking layers shows overlaps on the 0 forest and Land not ice layers.
I'm concerned about accidently changing the shape Unite icon to merge all the pieces of artwork together. Uniting at times changed the opacity and adds quite a bit of production time to my projects.
Looking forward to a solution for this.