Here was my post about random engraved lines and it ended up being overlapping/touching nodes that were the issue, not open paths. The crazy thing was not every overlapping set of node caused a separate random line; if I removed the set of overlapping nodes causing the issue, the line just jumped to another set of overlapping nodes. The same file may or may not produce the error when processed either and I never figured out the pattern when it would work correctly. The whole thing really ticked me off so I literally spent hours checking every single flippin node in my complex plaid file and I ran dozens of processing tests. In the end I was able to fix and recreate the issue at will.