Hello haimat,
I have a few questions for you that will help narrow down what issue it is that you are experiencing.
Quick questions:
Since we have updated to 4.11 our UMG menus don’t scale well in all cases any more. For example, look at this image, a sample project running in windowed PIE mode:
As you can see, there is a nice white border around the message box. Now after resizing the same window only for a few pixels, the white border is gone:
Interestingly, when I change the window size via the mouse for another few pixels, sometimes only parts of the border disappear:
Very weird. Usually it works fine when running in full screen mode.
Any ideas?
Yes I can reproduce this problem even with a clean project. I have created a demo project here: Demo Project. The problem seems to be somehow related to the Margin value of the background image used in the MainWidget UMG asset.
Hello haimat,
I was able to reproduce the result that you are seeing on your end. However, after adjusting your margins for the image I was able to get it to render as intended. I believe this to be working as intended. I have provided the adjustments below. I hope that his information helps.
Adjustments:
Make it a great day
Hello haimat,
After looking over your project, it appears that this is working as intended. I was able to reproduce this results that you are seeing, however after adjusting the margins for the image I was able to have it render in what I believe is the intended fashion. I have provided the adjustments below. I hope that this information helps.
Adjustments:
Make it a great day
Hmm, it’s a bit better with your settings. But sometimes the white border line still disappears on one or two sides 
Hello haimat,
Using the suggestion above the issue no longer appears to happen on my end. You may need to adjust your margins to better suit the result that you want. I hope that this information helps.
Make it a great day
Hey Q, we have the exact same problem, since we’re using thin lines too(1-2pixels) in our UI.
We’re tried different methods, but even the more stable one, still do the same thing as mentioned above.
Is there any recommendation, advice, maybe example of best practices to fix this issue? Besides what you’ve mentioned above, since it doesn’t really helps, and it actually the least good way of doing that, in our experience.
The quote on quote “better” method is to make it one texture, border, background, etc, one solid texture with the size of the UI window, but even that makes lines thiner\thicker or completely disappearing if line is 1pixel on some scaling values.
I’ve seen that fortnite UI have some thin lines(selected inventory item), I wonder how it behaves on different resolutions(if there is any dpi scaling).
