The oscar is prone to getting vapour lock, and therefore not getting up to proper temperature. After heating it up, open the steam valve completely to release locked vapour, close valve and let warm up further. Normal use for me on first heating is - turn on, leave for 30 minutes, open steam valve let it blow clear for a minute, close steam valve and let warm up.
The oscar relies on a pressuer sensor for getting to the correct temperature, and cannot get up to proper temp until the vapor lock is removed. Ive always found it strange that nuova didnt spend an extra few dollars and add a vacuum breaker to the unit.