I have a similar problem to donbassopera with a StudioLive 32 Series III and Firmware v2.1.16232. My Solo Edit is set to Latch and Pre Fade Listen is off. Normally there is no sound to start with and the headphone sound may start after a few minutes after power on. Sometimes it will stop during a session. I too seem to get it to clear after randomly pressing buttons on the Solo Edit page although this is not clear cut. It could well be related to the project/scene firmware change but I am not definite about this.