I encountered an issue in act 4 regarding the buttons that reveal a secret. Prior to patch 63 it didn't happen, but now when I press the button and the secret turns out to be a shop/merchant NPC then I'm not able to interact with him/her, the dollar sign icon simply doesn't appear. I have to close the game and restart it to be able to buy stuff.
I'm playing single player, therefore I don't know if it's the same case in multiplayer.