As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE AT FL350, RECEIVED AN INDICATION ON EICAS AND MFD THAT THE AFT SERVICE DOOR WAS OPEN. BOTH LATCH INDICATORS ON THE DOOR WERE GREEN AND PRESSURIZATION WAS NORMAL. THE INDICATION BECAME INTERMITTENT AS THE FLIGHT PROGRESSED. R & R R2 DOOR PROXIMITY SENSOR, OPS CHECKED GOOD IAW AMM 52-74-21.