I have an "unread" reputation change on the activity tab of my profile. This breaks the border below the tabs.
Browser: FF 68.3.0 ESR
OS: macOS 10.14.6
When changing from tracking a tag-badge into tracking my next privilege the issue disappears, only to re-appear when the selection is reversed. Opposite to this, now fixed, report: Border bottom is missing for some items in Activity tab in Firefox