Hi Admin,
Hope you're doing well.
- Are there any errors in "Event Viewer"?
- Confirm that there is a backup and try to rebuild the virtual machine.
- Make sure that the Integration Services are installed and up-to-date on your Ubuntu virtual machine.
- Due to the limitation resource of forum, we cannot collect more logs for further troubleshooting, you can choose to go to the Microsoft Customer Service Center to open a new ticket so that with their permission level and resource, Microsoft could provide you with better help on your request.
Best Regards