rhythmic slash notation plays the entered notes

Some odd behavior with 'toggle slash rhythmic slash notation'. By default I understand that whatever notes and rhythmic values I enter first, before toggling, are not supposed to playback when the bar(s) are toggled to rhythmic slash. In some places in my score it works like that. The Cmd-K chords play with no note sounding, but in other places, the notes play along with the cmd-K chords. My entry process is the same thorough out. What am I missing? Many Thanks!! [Mac 14.6.1 / MS 4.4.1.2]