KS10 switches into unwanted T-coil mode

My KS10’s (still working fine, btw) have a habit of switching into what the EasyLine program defines as their “Public T-coil +Mic” mode, accompanied by loud buzzing. I have to go into EasyLine to swipe it back into “Automatic Premium.”
Is there a button maneuver on the aids to accomplish this switch? Why does it happen in the first place ? I do have a portable phone with T-coil nearby.