After its first significant overnight rain, our 2020 Defender leaked heavily on the front passenger side. There was no evident moisture above the dash. Water was running down from under the dash adjacent to the passenger door. There was large, deep puddle on the mat. Anyone had this problem yet? Our windshield has already been replaced once by the dealer after rock damage.

 

This is the first significant rain since they replaced the windshield? That's most likely you culprit right there, they screwed up the seal when they installed the new glass.

 

Did you find out what this fault was please, as the exact same issue has now happened to us on the same vehicle?

 

It could be the windshield but I’m also wondering where the drain channels are and maybe they’re clogged? Just a thought but not sure where they are on this rig. But worth exploring nonetheless.