Vertical lines are still quite buggy

[DakshG07]

Occasionally hitting Preprocess multiple times will bug out some of the vertical (90 degrees rotate, undefined slope) lines. I've tried to figure out and I have no idea why, and I can't reproduce this error reliably enough. Occasionally, however, these vertical lines will flip the direction they are facing and throw everything off screen. This could probably get annoying with more complex paths, but I've got no idea how to fix it.

[DakshG07]

For now, I've decided to only allow one press of the Preprocess button without any edits. Hopefully this makes the issue much more obscure.