Water leaks in the main, are difficult to work out where they come from.
if the windscreen us moved when the direct glaring PU is not totally cured can cause leaks, also if the bead is not the right profile that can cause an area where it can leak
other things,
sunroof drainage pipe being blocked.
one of the rubber grommets between the engine and the cabin missed out or not fitted correctly
seam sealer not applied correctly to a joint
rubber seal not fitted correctly
the drainage holes from where the body was put through electro coat not sealed correctly afterwards causing water to wick up into the cabin
Heater or air con pipe not correctly fitted.
tgere is also an issue where some cars don’t have a drainage channel on the roof and cars with the door frame tgat goes over the body
water ingress is a science lol