As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORT: ATC REPORTED STUCK MIC IN FLIGHT UNABLE TO COMMUNICATE W/ATC CAUSE UNDETERMINED ALL RADIOS. SAMC TEXT: F-O WAS USING THE RADIOS. COULD NOT XMIT OR RCV UNTIL OBS AUDIO PANEL WAS USED. SWAPPED WITH OBSERVERS AUDIO SEL PANEL, ALL VHF OPS NORMAL.