Cards that are allowed more than 1 of in brawl (And I assume 4 of in other constructed sets, I have not explicitly tried) are registering as invalid. I have a Tempest Hawk deck and a Nazgul deck and both are now invalid this morning due to having too many of those cards in their respective decks.

To recreate, create a deck and add 5+ Nazgul or 5+ tempest hawk.
This is on the PC client.
The decks do not appear when you want to chose one to play, and appear as decks with errors when viewing your deck collection.
They should be valid decks due to the rulings on the cards superseding the restrictions of the rules of the game.