Changing of UPN in AD/AzureAD causes separation and sync issues with OneDrive for Business. No other Office 365 application appears affected. Currently no way to force a UPN change on the OneDrive side and we are being told that re-syncing the library is the only way to fix the issue.
Why has voting been closed on this? I want to change UPN for 200 users and the prospect of having them all re-sync the libraries is frightening!