Starting to sound like these have a mind of it's own.
I had another odd experience too. I took the phaser through each setting 0 - 9 and then went straight back to 0. When I pulled the trigger, instead of getting the "click" sound, I got what sounded like the bridge communicator or some other random bridge sound. I turned the knob away from 0 and it went away. I tried recreating it but couldnt.