On 25 September 2020, a Sikorsky S92A returning from an offshore platform was in descent approximately 40nm from destination Stavanger when main gear box low pressure and left engine oil temperature cautions were annunciated. The affected engine was reduced to idle and a MAYDAY declared. A further related alert prompted descent to 200 feet and sixteen minutes after the initial malfunction, a normal landing was completed at Stavanger. A significant oil leak found in the main gear box was attributed to oil flow reduction and consequent overheating caused by a loose washer inadvertently left inside the gearbox during routine maintenance.