I did a quick search and couldn't anything regarding this. Sorry, if it is redundant.
I noticed some side effects when undoing Lead-in scale changes.
Easiest way to reproduce: Fire up TG2. Go to the base color shader of the default project. Change Lead-in Scale from 1000 to 100. Undo the change (via menu or short-cut). With every change-undo-circle the Noise octaves are increased and, as a result, the Smallest scale is decreased.