Tried card trader in a Cerberus deck and either the card proportion are screwing up the algorithms or there's a 1 in 3 chance card trader does nothing and I get the same card back.
There was testing in duel links and when decks are shuffled the card you draw isn't really random - that may be a reason why sometimes when you use switcheroo or card trader you get the same card.
There was testing in duel links and when decks are shuffled the card you draw isn't really random - that may be a reason why sometimes when you use switcheroo or card trader you get the same card.
There's a 25% chance of receiving the same card back in Switcheroo, assuming the same mechanic is in place for the Card Trader, it would explain what you're seeing.