Doesn't matter - it's not watertight anyway.

As said, heater matrix may be the issue - check to see if the cars water needs topping up; dead giveaway to leaking matrix.

Also, check the drain holes under the scuttle - if these get blocked the water backs up and finds another drain point; usually into the car through the bulkhead. Just had EXACTLY the same thing happen with a Galaxy screen we replaced - after three new screens it was still doing it, so I took the scuttle off, pointed a hose at it, and watched the water back up out the drain points, and find a gap in the bulkhead to flow through - leaving a swimming pool in the passenger footwell.