Try this sample and if you are still facing any issues,
please share the sample in which the issue is reproduced or modify the given
sample. We found you have been used the custom save method in server side so
please share the code snippets you have used in the SaveDocument method. This
will be helpful for us to analyze further and provide the details.
Note: Make sure that you are using the same client and
server versions. For the client-side, you need to update the respective version
CDN links in the _Layout.cshtml. For the server-side, you need to update
the Nuget Packages.