That’s normally a compile time option for grbl. Have you changed the firmware lately?
$3 would not change it.
$# gives you the G28 position.
There is a compile time variable that controls the quadrant that programs like UGCS report. Of the many versions of firmware that appear the switch keeps bouncing back and forth depending on who builds it.
Be careful, G28 uses machine co-ordinates, not work co-ordinates.
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