As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EVAC ALARM HAS ACTIVATED AT ALL STATIONS ALL BY ITSELF. PRESSED HORN SHUTOFF, NO HELP. [SUP 06-14-07] TESTED EVAC SYSTEM PER UA ENGINEERING SPECIFICATIONS. SYSTEM TESTED GOOD. NO DEFECTS NOTED. UNABLE TO ESTABLISH ANY CAUSE FOR THIS IRREGULARITY EVENT.