The Last.fm importer manually steps through your listen history and imports the listens one page at a time. Should it fail for whatever reason, it is safe to restart the import process. Running the import process multiple times does not create duplicates in your ListenBrainz listen history.
I had to stop and start the importer. My browser was non responsive. I thought from the above text that the import would pick up from where it left off, but it started right back at page 1 of 3500. The actual importer says:
Sending page 973 of 3569 to ListenBrainz
Please don’t close this page while this is running
Which is clearer but not perfect. How about:
“Closing this page during import may require a full restart of the importer from the beginning.”
Or something? (Do I make a ticket on the tracker? How do I know what goes there vs. here?)