This was the initial preliminary report:
For the present, our conclusion is that the engine failure was directly caused by low oil pressure. The level of lubricating oil in the tanks was within set limits, however relatively low, when the vessel started to cross Hustadvika. The tanks were provided with level alarms, however these had not been triggered at this time. The heavy seas in Hustadvika probably caused movements in the tanks so large that the supply to the lubricating oil pumps stopped. This triggered an alarm indicating a low level of lubrication oil, which in turn shortly thereafter caused an automatic shutdown of the engines.
This was presumably after some investigation so it’s a mystery why the conclusion has changed so much.