My machine is not cutting square it is cutting a parallelogram please help

I am needing some help I am in the process of trying to make some dice trays for d&d players and when I cut my prototype my machine is supposed to cut the parameter but the lid and the base are both out of square each side is square to each other but they are making a parallelogram I rolled my machine Gantry to the front to make sure it was still in square which it is can anyone point me in the right direction to fix this problem thanks in advance

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