u/Legal-Potato-3217

Has anyone else ever had the same problem where they already have enough cards to upgrade a character, but they're just waiting for money, and then when they finally get the money and want to upgrade, they lose cards? It's happened to me four times already, and only in this season and the last; it never happened before. In the Dark Prince, they only took one card, but in the Mirror, they took 35... and no, I haven't donated them. I'm careful not to, so why is this happening?