Can't move measure to previous system

A Google search returned years of user frustration with MS's inability to simply move a measure to the previous system, and I'm hoping for some new insight. I'm transposing a piano/conductor score, and the layout must be identical to the original. The system containing m 57 should have four bars: 57, 58, 59 and 60. Setting the score to 4 measures per system has no effect. "Remove current systems breaks" has no effect. The "stretch" feature { } will not force the measure to snap to the previous. I'm running MS 3 on a Mac Air M1 chip.