As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAS - DLH - CREW REPORTED THE FIRST OFFICERS TRANSMITTER INOPERATIVE ON ANY MIC. AIRCRAFT RETURNED TO LAS AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE FIRST OFFICERS OXYGEN MASK SYSTEM CAUSING DISTORTION IN THE FIRST OFFICERS COMM. REMOVED AND REPLACED FIRST OFFICERS OXYGEN MASK BOX ASSEMBLY IAW MM 35-10-04. COMM OPERATIONALLY CHECKS NORMAL. AIRCRAFT RETURNED TO SERVICE.