Machine not moving south along 'y' axis

The overall limits would certainly apply to the original Y axis, but swapping the stepper driver controls should rule that out.

Having had time to think this over, perhaps the Y axis limit switch has failed.

The Ruida controller should have a Diagnostic display showing the state of the input signals; on my KT332N it’s hidden in Menu → Diagnoses. Manually triggering each switch should produce a corresponding change in its indicator.

A previous discussion goes over that process: