Techsys and I did some experimenting a while back on this. I updated someone else's tracker issue, I could probably dig it up after 7 PM EST if you wanted.
Anyways, it's worth noting that if it runs like "\", you get significantly different results than if it runs like "/". One's broke, the other is fine (don't remember which off the top of my head). Horizontal and vertical are both fine. If you have it at the proper angle to reproduce the bug, then and only then does it matter where the starting point is, with the result of it being closer to the vertical or horizontal. It's quite noticeable if you're attempting to place mines at around a 45 degree angle.
We were able to consistently reproduce it.
As to the mine spacing, I rather inconsistently but frequently reproduced it, often within minutes in the same session. It might be related to zoom, but I couldn't figure out anything conclusive, just a hunch.