Unfortunately Pandora has made no moves to fix the bugs in ranking/hours listened loss. It's definitely not a client issue because you will find the exact same loss of data across different platforms including smart phone apps, and different web browsers. Because of the loss, I've been looking at soundiiz to backup all my Pandora stations. It's not ideal because it doesn't backup play counts or hours, and doesn't do exact matches (I had a lot of mismatches on Christmas music). With a backup at least you won't lose everything next time Pandora does another "oops".
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