Still fiddling with RoboRealm, and getting inconsistent behaviour with the Straight Lines module in 18.104.22.168. The basic symptom is that in certain circumstances it will only detect vertical lines, ignoring all horizontal ones.
With the uploaded file, doing a Canny it's fine, but use a Sobel (All), or leave raw, and run Straight Lines, then only verticals are picked up. Insert a Rotate 90 deg. between the Sobel and Straight Lines, and completely different parts of the image are detected!
Also, while playing with this I noted that the edge artifacts which disappear with zooming -- that you just looked at, appear in all their glory...
Thanks for listening,