This error is related to the Veeam console UI (WPF/Ribbon), not to the backup engine itself. It happens when the visual component tries to open or position a dropdown/menu and loses the window context, common in RDP sessions, multi-monitor setups, resolution changes, or Windows DPI issues.
you can try close and reopen the Veeam console, reconmect the RDP session, temporarily set display scaling to 100%
If the error persists, it’s best to open a support case with Veeam so they can review the logs in detail.