As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE TOILET CAUTION. WHEN ON APPROACH. APU WAS RUNNING. RAN QRH PROCEDURE AND MESSAGE CLEARED. COULD SMELL BURNING SMELL IN THE COCKPIT. THE SMELL DISSIPATED AFTER THE QRH PROCEDURE. (FLT#4990) FO: 01/29/2019 CLOSED REMOVED AND REPLACED APU ASSY. LEAK AND OPS CHECK GOOD.1