Found it in my case...
Was a blocked drainage pipe of the sunroof. Save you the trouble of looking for through the service manual...
Removed front passenger pillar cover (There's a clip up the top, slide a flat screwdriver down to unclip)
Took out the Centre light above the rear view mirror (lens pops with flat screwdriver in the 3 tab spots across the bottom/windscreen end, remove 2 screws).
Removed passenger sunvisor (just pop the caps and unscrew, sunvisor holder just pops with flat screwdriver inserted into each).
Removed passenger grab handle (Remove caps, remove screws, pull out left side then spin entire handle counter clockwise to pop out).
Remove Trim around interior of sunroof.
The roof then was saggy enough I could reach in... I pulled the drain pipe off which resulted in a slight downpour... which happened to aim and run straight to my crotch
But then i put it back on and pinched the pipe at the sunroof end then squeezed it to force some water down... was enough to dislodge the blockage and the car farted at me in recognition as the water drained (it literally sounded like a fart)... If you had a pipe cleaner or something it'd be better but I had nothing on hand so for now that'll do. mMight put some dishwashing detergent in it or something.
Now putting back together... in the rain. But at least it'll be dry on the inside now. Quite possibly your issue too, maybe you're parking on a slight lean towards the Driver's side, hence why it is leaking more on that side. Either way the drainage pipe is on the passenger side.
Hope this helps.