As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO TRANSMIT VOICE OVER SATCOM. SIDETONE WAS HEARD BY BOTH PILOTS. RECEIVE AND DATA OK. GROUNDED - YES. COULD NOT DUPLICATE ISSUE. PERFORMED GOOD RADIO CHECK CALLS W/ DISPATCH UTILIZING SAT 1&2. OPS NML REF B737-900 AMM 23-15-00. ETOPS GND VERIFICATION TEST SUCCESSFUL.