Excel 2016 copy/paste issue is back after KB5002934 update

Your report describes a recurrence after KB5002934, but the timing alone does not establish Microsoft’s internal explanation or confirm that the September fix was removed. Microsoft’s KB5002665 article now says an earlier package could still fail with conditional formatting and directs customers to its latest revision.
First record Excel’s exact file version, architecture, MSI versus Click-to-Run installation, and installed update revisions on affected machines. Test a minimal workbook with and without conditional formatting. On a representative test workstation, evaluate the current applicable Microsoft package and verify whether paste works before wider deployment; do not assume an older package should overwrite a newer security update.
Meanwhile, test Paste Special options such as Values or Formulas where they preserve the required content. Keep security-update removal a documented, risk-reviewed exception rather than a permanent script. Submit the reproducible workbook and version comparison through your organization’s support channel for an authoritative regression assessment.