I agree the mount is a retainer only. I would expect the runout of the screw rods needs a little space to operate. The linear bearings take up the non-axial loads.
I think there should be some end play and it seems the Y2 rod doesn’t have enough.
You can feel the vibration in the mounting block.
Can you move that end of the screw rod on your machines ? It’s not a lot, but you know it’s free.