Visual header containers (three white squares) appear on slicer visuals across all reports

I am experiencing a visual regression where visual header containers (three white squares) appear when hovering over slicer visuals, even when all visual header options are disabled.

This issue is not isolated to a single report and not caused by recent report edits:

• The behavior now appears in:
  • Multiple PBIX files
  • Including older backups stored on our network
  • Including reports that have not been opened or modified recently
• This strongly suggests a Power BI Desktop / rendering regression, not report‑level configuration or authoring actions. They appear in the desktop version and the published report.