Technical air in fuel filter

[Filberworce]

Hi, I've got a 2011 2.0 Scudo which has developed the habit of getting air in the fuel filter after it has stood for 3 hours or more. Once I've bled the filter it's fine and pulls well with no missing or hesitation. I've changed the filter and o ring without any change has anyone got any ideas of where to go to next?
Thanks