ION xe level wheel behavior changed itself like bad magic/ Cannot find

Our issue is the wheel behavior changed itself between shutdown Friday night and Start up Saturday afternoon. 
I believe I carefully searched manual v3.1.1 and can find no place that addresses wheel sensitivity adjustments, which means I'm probably a bad searcher ! It apparently used to be in Setup/ ... Face Panel but now only encoders are there .
Our change went from smooth fade up/ down at any speed to smooth when moving slowly and jumping stair step style at any other rotation speed..

Is there some exotic key combination that changes the level wheel's behavior ?

THANKS FOR READING !

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