Have had water coming in for ages top left corner inside windscreen, dripping over to driver position, read several threads and thought sunroof was leaking, so when dry I taped up sunroof with thick plastic and duck tape no way was any water coming in there, to my surprise next day after rain a wet patch in top left corner again.
That was not from sunroof, so checked windscreen seal and saw it was rather loose in the corner, bought some black silicone lifted seal filled with silicone and also the outside area to which the gutter drains. When cured wet thoroughly with hose pipe and no leaks at all, took A pillar cover off to check and all bone dry, did the driver side also just in case, so glad I did not go to all the trouble of taking headlining down etc.

If it is anything like mine you will end up with silicone all the way across the top of the window. I put a little bit under passenger side rubber,after a few weeks the rubber started to lift, so more silicone,more lift etc etc.