From my medical background sounds like one of the crew may have become unwell, supplying O2 is the first line of response in a first aid situation, the re breath bag with the o2 cylinder is more beneficial to the 'patient' then the drop down o2 masks in the deck as these require the person to be spontaneously breathing
If the aircraft is back in service today seems like can't be much wrong with it and with the paras first on board it seems to back up my theory