I was trying to rewatch one of my saved replays and noticed that while the replay was going, the cards were having stat changes on the fly, some cards were disappearing despite nothing being played to remove them, the ATK stat was as low as 4 or as high as 547,293 (or similar absurd numbers) the monster card type was showing as if a single card was being treated as a fairy type. There were times when the incorrect cards were being affected by effects that activated in response to another card. (for ex. card A activates, card B negates card A and attempts to destroy it, but card C that wasn’t involved in the chain got destroyed and card A lingers on the field). The level stats were changing randomly and some cards in hand were sitting in defense mode… I even saw a ritual spell become a pendulum card with no scales or pend. effect (this one is purely a visual bug tho).
Its an unreversable bug due to the game core having some bits changed in the latest update, resulting in bugs as the client tries to recreate the duel during the old replays, calling on old bit values, which lead to strange results.