On 17 January 2018, two Airbus A320s both inbound to Surabaya at night were vectored to the same waypoint to hold, one at FL210 and the other at FL200 but the one initially given FL210 was then re-cleared to also descend to FL200. The two aircraft subsequently received and followed coordinated TCAS RAs which restored prescribed separation. The Investigation found that before the conflict, the experienced controller involved had made several transmissions to aircraft other than the intended ones and noted that the usually-available ATC conflict alerting system had been temporarily out of service without any consequent mitigations in place.