Caused by Bug 1481677. When switching the search bar to a fixed header we need to add some top padding to make up for the space where the search bar is in the content while scrolling. We cant add that padding if there is no search section.

Commits pushed to master at https://github.com/mozilla/activity-stream https://github.com/mozilla/activity-stream/commit/aab3771a50215d97ed4f34c7056f46a0f943a822 Fix Bug 1482184 - only apply fixed-search if search section is visible https://github.com/mozilla/activity-stream/commit/e4b2ac4af96481ee6b4bd4bbb2c2ff6d3213ade0 Merge pull request #4304 from rlr/bug1482184/scroll-fix Fix Bug 1482184 - only apply fixed-search if search section is visible

qa note: this regressed from bug 1481677 which never made it to nightly in its own export, so you can't verify that the bug exists with an earlier nightly.

I'm marking this issue as "Verified Fixed" based on comment 3 and on the resolution from Bug 1481677.

Marking the issue as verified on Beta 62 as well, based on comment 3 and the verification from bug 1481677 comment 6.