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 avoids the motors to move freely and can sometimes even block it completely.
2. Origin
This assembly problem is due to when you placed the gantry, it's caused by the feet not being square to the frame anymore and thus the motors being too high.
3. Solution
Simply loosen the feet, set them lower and square to the frame and retighten all the screws.
