Guys, I think I found a work-around that worked for me.
In my case, I wanted to expand the vector boundaries by 1px. What I found is that when I set it to 0.5px (used the “outside” option) the bug didn’t occur. Then I Outlined > flattened and applied the same process to the new vector. It worked again!
The result was that at the end I had a 1px path-expanded vector.
I have the same issue for a while now, over a year I’d say. Sometimes cleaning up some paths helps but nothing really obvious. I tried reducing it from 3px to 1px line and it worked but when I added a stroke to that 1px and tried to expand the lines, same thing happened. No choice but to tediously export as SVG, bring into the all-mighty Illustrator to expand the path, merge and copy and past back into Figma.
This is a long standing bug that our engineers have been continuously logging and trying to fix. This generally only happens on icons imported from other apps, where the mirroring on the points is reversed or missing.
Right now, the best workaround is to rebuild affected icons from scratch. Please note that redrawing with fewer points can also help.
While we can’t guarantee an ETA on a fix/improvements, please know that our team follows this thread and takes everything you provide into consideration.
I’m glad that you know about this issue and you’re working on it. However, it’s been there for many years now and it’s sad that it’s still unresolved. I’m wondering why other vector apps don’t suffer from the same issue…
I’m working with some icons now and it happens to literally half of them. Very annoying because I have to use a different software, because Figma would be otherwise perfectly capable of handling these simple edits.