According to this Behind the Glass podcast, Porsche are treating the driver’s window and driver’s side rear window as a warranty item.
This issue, according to Sam, seems to be the rear glass is thin and can crack if too much weight is applied to it.
His supplying dealer Porsche Guildford say the cracking of this window is caused by the driver’s window not being correctly aligned and hitting the rear window.
Tony (in the same podcast) also highlighted the fact that the driver’s window can also be cracked if the door is opened too quickly after coming to a stop. This again appears to be a known issue and Porsche are replacing the windows under warranty.
While we are on the subject of build issues with the 992 GT3
Same had an issue with one of the rear driveshafts not being securely mounted to the diff from the factory which led to the driveshaft completely detaching itself from the diff.
And Tony has an issue with one of the rear dampers leaking, which at the time of the podcast had not been resolved ie under warranty.