No, they were engraves. There were no duplicate shapes on top of each other and no open paths. (I literally inspected each and every node.) However the corner of several of the shapes had two, sometimes three nodes stacked on top of each other or so close they were touching. For whatever reason, the nodes being on top of each other caused the error. It looks like the GF incorrectly interpreted them as an open path. The weird thing is not all the stacked nodes in the file caused random lines: there was only ever two error lines and there was 15+ corners with stacked nodes. When I would fix one set of stacked nodes, the GF would just add the line to another set.
Even stranger, the very same elements with stacked nodes was used in this engraving. (I had just cut the file down and enlarged it for the other engraving.) The stacked nodes caused no processing errors in this one at all.
