Firstly what screen is it?? Fixed or tip-out?
If it's fixed screen, are the hinge holes blocked and sealed off.
The fixed screens also can leak from the top seal against the frame, something in manufacturing is off and the glass and metalwork curves don't match, leaving a gap in the middle on some. Either add extra sealing strip or mastik the top edge.
But also check it's not coming in via the wiper motor, the external plastic trim isn't sealed and water collects behind it and ends up coming in the hole the wiper passes through.