A Logic Error (ロジックエラー Rojikku Erā) is the worst mistake that a Game Master can make, being a contradiction in the tale that they've created. When a Logic Error occurs, the Game Master can either fix it or admit their mistake, with the latter case resulting in the game board immediately being destroyed. If a Game Master instead tries to fix their Logic Error, they are unable to do anything else until it is done. Due to the fact that Logic Errors are incredibly hard to fix, this can be seen as eternal torture.
Both Bernkastel and Lambdadelta have suffered through Logic Errors; Bernkastel's case specifically demonstrates that Logic Errors can be forced on a piece by a Game Master. Bernkastel was given the responsibility of solving the Logic Error without even knowing it, and after succeeding she became the Witch of Miracles.
The only Logic Error seen and explored in detail is the one caused by BATTLER and Erika in Dawn of the Golden Witch. BATTLER wanted to make his piece version fake his death and escape a locked room, but unbeknownst to him Erika had retroactively sealed the room with duct tape, and this was not revealed until after BATTLER had declared that he wasn't inside the room with red. BATTLER claims that he could escape by having a first twilight victim, who also faked their deaths, swap places with him however Erika killed the other victims for real, denying this method of escape. Thus, BATTLER's mind was trapped inside of a similar room, his goal to escape the chain-locked room while the chain was still intact.