Duplicate Protection Not Working
Today, I purchased FDN packs with gems I paid real money for. Duplicate protection was not working and I recieved duplicates of cards that I completed or had some of in earlier sets. Support told me to post here, even though this is a purchase that needs addressed and not just a bug report.
I now have
5 Giada, Font of Hope (4 SNC, 1 FDN)
5 Doubling Season (2 some old set, 3 FDN)
7 Painful Quandary (4 TBW, 3 FDN)
7 Phyrexian Arena (4 ONE, 3 FDN)

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Rezzahan#77802 commented
Duplicate protection applies to cards from a single set. As you have shown in your picture, you don't have 4 of the Phyrexian Arena from Foundations yet. If you were to open one from Phyrexia: All Will Be One, THEN you would get a different card instead, because you already have 4 of that version already. The duplicate protection does not apply across sets.