The aircraft involved was a B747-400, ZS-SAW. It couldn't have been too serious a problem as that same aircraft left this morning for Mauritius , followed by another aircraft, an Airbus A340-200 about half an hour later. Seems to be a busy time of the year for pax to Mauritius.
Perhaps the crew simply ran out of duty time to complete the flight yesterday after the aircraft was repaired as the same crew does the outbound and return flights. This is probably close to 10hrs in total.