A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Since uninstalling KB5002934 restores the affected Excel functions, I’d check whether the issue occurs on multiple computers and whether they have the same Excel 2016 version and other Office updates installed.
Before rolling back the security update across more devices, I’d document the exact copy/paste and formula problems, along with the Office build number and Windows version, and report them through Microsoft Support. I’d also check the update’s official Microsoft documentation for known issues or a newer replacement update.
For now, I’d avoid assuming KB5002934 is the confirmed cause until Microsoft investigates, even though your uninstall test strongly suggests a connection. I wouldn’t recommend leaving the security update uninstalled long-term without an approved mitigation.