It looks like they were waiting for connecting passengers from both SQ713 (ex-BKK), which was running about 3 hours late, and SQ242 (ex-SYD) which was running 2 hours late.
SQ231 (SYD), SQ255 (BNE), SQ346 (ZRH), SQ366 (FCO) and SQ402 (DEL) seemed to be the affected flights.