Hi,
Please provide below information and do the following test first.
- What's the os version of your users' machine?
- Open PowerShell as administrator and run "get-hotfix", share the KB informaiton so that we could check if there is any update installed will cause the issue.
Test
- Generate a new excel report with a little simple date and tries to copy the data and paste value without format. Please see if the issue persists.
- Choose one local machine of user to uninstall Office 365 and install office 2016, try copy data again to see if the issue persists.
Thanks,
Eleven