Too many error for user to click through when syncing decks

[c-okelly]

User complaint: I've been using this add-on since the beginning of this year, and so far it has worked wonderfully. However, after the most recent update I get an error message telling me I have a duplicate card whenever I sync the remote decks. This wouldn't bother me too much, but it warns me for every single card that it syncs, and I have over 1000.