The spacer turns after the fingers close

Only after lifting in the video. I should have said that more carefully; the tray hides the lower part of the fingers until then.

Have maintenance inspect the contact faces before more teaching. Uneven grip can hide behind the tray.

During the isolated inspection, maintenance found one finger pad separating from its backing. The front looked normal. They have taken the gripper out of service for repair.

There's your visible defect. Who checks the altered points after the pad is replaced?

Our integrator reviewed those changes and verified the repaired setup. The block now leaves the tray squarely. We added pad condition to the maintenance inspection.

Useful result. Put that underside photo with the inspection notes; the intact-looking front fooled you once.