This is a minor but strange issue.
The problem is the vertical scroll bar is painted with the solid background color of the page.
I can reproduce the issue with the following conditions.
- Safari 2.1.1 on macOS 10.14.5 (No issue with Chrome 75.0.3770.100)
- Both web server and live preview
- On a particular page (and the localized version which is almost the same) on my site
I suppose this might be a bug of Safari but also suspect my Sparkle file is partially corrupted.