If the initial warranty scan succeeds, but the next one fails, previously scanned warranty data will still be listed on the asset page. Not sure this is something development would really want to change, as keeping the old data seems preferable in most cases. If your Lansweeper server is temporarily unable to connect to the manufacturer's website, previously scanned warranty data will not be removed.
A workaround would be to delete the data (manually or through a script) from the database tables below. (Proceed with caution and create a database backup first.)
- tblWarranty
- tblWarrantyDetails