Loose Clamps

I am cutting a 45 degree angle for the diagonal holder for the rebuild of my little telescope.  Here is some video.

It was running rough, loosening the workpiece from the screw holding it to the tilting table.  Why?   The tilting table was rocking slightly.  One of the T-nut clamps had been cross-threaded and was not locking the tilting table to the mill table.  Movement caused vibration, which loosened the workpiece.