Thank you for the feedback. It's possible that the issue lies with the files themselves or their permissions. Right-click on the MKV file, select "Properties," go to the "Security" tab, and verify that you have full control or write permissions for the file. You can modify the permissions to grant yourself the required access if necessary.
Create a backup copy of the MKV file and attempt to edit the metadata on the copied version. Sometimes, the original file may be locked or have specific attributes that prevent changes, but copying it might resolve the issue. If possible, try converting the MKV file to a different format, such as MP4, and see if you can successfully edit the metadata of the converted file. Some tools may have better support for metadata editing in specific file formats.
The MKV file itself may be corrupt or have issues that prevent metadata changes from being saved. Try playing the file in a media player to ensure it's working correctly. If the file is corrupted, you may need to obtain a new copy or consider re-downloading it.
If none of these steps resolves the issue, it's possible that the MKV files have certain properties or metadata settings that prevent them from being edited using the tools you have tried. In such cases, you may need to explore specialized MKV metadata editing software.