As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3356 - ATB - RETURNED TO BOS FOR FWD CARGO DOOR OPEN INDICATION. PRESSURIZATION WAS NORMAL. CREW REPORTED FEELING A VIBRATION. CORRECTIVE ACTION: REPLACED PROX SENSOR 6MJ ON LOG 5791144. AND DEFERRED PER MEL 52-71-01A-AND RETURNED AIRCRAFT TO SERVICE.