Strange white borders and wrong scrollbar position

[stalkerg]

I tried Firefox Night with enabled WebRender on my website and saw some artifacts.
I have:
Firefox Night 62.0a1 (2018-05-27)
Windows 10 64bit,
Video card: nVidia 1060 with driver 397.64
I have not so popular by DPI screen - Dell UP2516 with 25'' and 2560x1440 resolution.
If I made not 100% of the scale some artifacts were going.
Website: https://anime-pictures.net/
On the screenshot, I show firefox with webrender and normal firefox.

You can see here under the right block with the chat messages the strange white line, also strange white borders in the title of the block. Also, scollbar shifted for a little.
How it should be look:

[stalkerg]

Extra screenshot with a highlight of problems:

[gw3583]

If possible, could you raise a bugzilla bug for this? It's easier to track there when it's fixed and exactly where the issue is.

[gw3583]

Did you have a chance to open a bugzilla bug? If so, we can link to it here and close this :)

[stalkerg]

Done: https://bugzilla.mozilla.org/show_bug.cgi?id=1474496
Sorry for the long wait! (I was too busy)

[gw3583]

Thanks!

[gw3583]

Marked fixed in bugzilla.