tfoot had position: sticky but no explicit z-index (auto/0), while the sticky month/year group-row headers use z-index: 1 -- so a group row scrolling past the bottom painted on top of the totals footer instead of behind it. z-index: 3 (above thead's 2 and the group-row's 1). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>