Grasping at straws for you.
1. With the side windows closed and latched push them forward to see if they open. The latch can be deceiving.
2. In darkness have one person shine a bright light in the generator compartment aiming up towards the floor and dash area. Have one person watch for light intrusion. If found, seal the area with expanding foam.
Again, just throwing out ideas.
..2016 Legacy 340KP SR340, 10,500 Miles..