Would illegally moving cards during a game from the sideboard to the hand/library or vice-versa be a Hidden Card Error or a Deck Problem? For example...
- A player is instructed to shuffle their hand into their library but accidentally shuffles their sideboard into their library instead
- A player is instructed to shuffle their hand into their library but accidentally shuffles their hand into their sideboard instead
- A player resolves the second effect of Mastermind's Acquisition without waiting for their opponent to respond, and their opponent wanted to counter the Acquisition
- A player resolves the Sorcery effect of Fae of Wishes without revealing that the card put into the hand is a noncreature
- A game is restarted via Karn Liberated and one or both players sideboard, believing they are allowed to do so (the error is caught on the first turn of the restarted game)
How should these types of errors be classified and addressed?