Make sure your music library is using the “Plex Music” agent, and is set to “Prefer local metadata.”
There are some things you may be doing in your embedded tags that can confuse Plex. This How-To article explains some of those:
[HowTo] Configure Plex to use embedded metadata (music)
If all that is correct, when you tell Plex to Refresh Metadata on the one album, it should use the embedded tags that it finds, and only get online info where local info isn’t available.
