If I search in the forum for this issue, I see at least two possible causes for the issue:
- some oddity in a file will stop the import process (e.g. see this post)
- instability in the network hampers the identification process (which communicates with Roon’s cloud services)
You might also try turning off the background audio analysis (Settings > Library) to see if that is impacting the import of what appear to be a large number of files.
Support will probably want to pull logs from your Core to see what is happening, so please leave it running if you can (even if it has apparently frozen).