At the end of the assembly, you are fixing your spoilerboard to the frame and you notice the Y motors (or the spacers) touch the MDF boards.
When EVO it travelling along the Y axis, that contact prevents the motors from moving freely and can sometimes even block them completely.
When mounting the gantry to the structure, the feet may have moved and not be square to the frame anymore making the motors placement too high.
Simply loosen the feet, set them lower and square to the frame and retighten all the screws.
