Air leakage and water at shoe molding under window

The rear end of my house has a bedroom and an office next two each other. During the winter, I can feel cold air flowing underneath the baseboard and shoe molding in the office but not the adjacent bedroom. During the summer, I can feel warm air in the same location. Today I noticed that the floor was wet next to baseboard. I'm assuming this is condensation. Both windows sit above a shed roof but the roof below the office sits on top of a bump out that is part of the interior conditioned space. The rest of the roof (under the bedroom) covers the back porch.

I had a home energy company come to do an audit. The inspector told me to remove the shoe molding and insert a backer rod or low expansion foam to stop the air leak. I was worried that there is an issue with the sheathing behind the shed roof. Would it be better to remove the bead board and place exterior foam against the sheathing? The only problem is that there is sheathing blocking the space under the office window.