We have created a block library - all blocks using same scale and units.
most blocks insert automatically at scale of 1 - but a few blocks automatically insert with a scale of 12. anyone know why?

Also it depends on units of drawing you are inserting in, check units in target drawing too, not only in block definitions, especially [VAR]INSUNITS[/VAR], [VAR]INSUNITSDEFSOURCE[/VAR], [VAR]INSUNITSDEFTARGET[/VAR].