You run a migration to SharePoint 2019 using Insane Mode that contains files with special characters such as # or %, and you errors on those files. These errors occur even when you updated to the latest version of the server extension.
There is certain instances where the server extension does not identify the SharePoint version as 2019, so it does not handle the special characters correctly. This results in errors with your files that contain # and/or % if the Allow Special Characters option in your migration settings is enabled.
You will need to follow these steps to fix the issue:
- Uninstall the server extension.
- Open the Registry Editor (regedit) on your server.
- Follow this path:
- Shared Tools
- Web Server Extensions
- Verify that the item named Version is present in 16.0, and that the number under the Data row is 18.104.22.16800 or higher.
- Reinstall the server extension.