This occurs on other pages as well, but it does not reproduce as a black page. Instead it feels like a screenshot or a previous framebuffer is blended with the new page. Example: https://news.ycombinator.com/item?id=21135424 go to ~ mid page, switch away from app, switch back and immediately scroll up.
Bug 1581868 Comment 4 Edit History
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~~This occurs on other pages as well, but it does not reproduce as a black page. Instead it feels like a screenshot or a previous framebuffer is blended with the new page. Example: https://news.ycombinator.com/item?id=21135424 go to ~ mid page, switch away from app, switch back and immediately scroll up.~~ This is no longer reproducible, so I'm assuming this was unrelated to this issue.