She means this one, which she posted after we realized you had found a new bug:
https://bugs.launchpad.net/inkscape/+bug/1687514It seems someone has posted a work-around, which I can barely understand myself. Well actually I'm going to have to ask what it means. But as soon as I understand, I'll tell you how.
Or meanwhile, here's the 7zip website, where you can download it.
http://www.7-zip.org/ (I was surprised that you mentioned finding it on MS Store, so I looked it up. When I search MS Store, it's not there. So maybe you didn't have the right program?)
For changing the Interpolator option, I found that changing it to almost any of the other options seems to fix it. But that one I suggested....well actually, I could not know if it made any change to the line, because I still can't see anything drawn with triangle in/out. So I didn't realize it was changing the appearance. I can see that CubicBezierFit makes a big bump on the end of it. Linear sometimes doesn't fix it.
To be honest, this technically isn't a fix for the problem. Maybe it's more like a work-around.
When you say it's making it darker, do you mean thicker or wider? Because you can adjust that with the pink node. Or if you mean a darker color, you can change the color of the line yourself.
I'm not sure what you mean by restoring the SVG file. Do you mean make everything visible again? I guess if you just delete all the lines that you made with powerstroke, it should restore it. Or if you just open the file by clicking on the attachment, the file looks ok to me. I can't find any invisible objects.
I'll try to find out what that cryptic comment means (I mean in the bug report).