2 options:
1) You have reached master 2 with Nod at least once. Once you reach a rank you get its rewards. If you climb there again after a season reset, the rewards are reduced. So the first time you climb to master 1 you get some epics, but when you do that again, you only get some gold crates. Please check if you have reached master 1 in a season before with Nod. If yes, everything is fine. If no, see below.
2) There used to be a bug where gold crates were displayed as epics. Maybe you have it right now. If option 1 didn‘t happen to you, try to get the crates and remember their contents. The epic one should drop at least 5 epic cards, the gold one should drop 0-1. You got correct amount of cards? Then you either reached this rank before or its a bug. You got incorrect amount of cards? Then its this annoying visual bug, but you should still get the correct amount of cards.
I still think its just option 1, check if you have reached master 1 with Nod in a previous season.
