St Gobain original suppliers - most windscreen firms offer Pilkington - have heard of issue with fit - but i suspect its the fitting rather than the screen, make sure it has the right spec - top tint, fm antenna (in screen), rain sensor (if you have rainsensor wipers) - the seal seems to be a challenge - rather than using porsche parts the main stream windscreen fitters use generic stuff they have spools of
best advice I was given was take it to a depot, rather than using mobile, and make sure you are happy with the screen before they start, also - take pictures of your wiper sweep, the fit of the current one (edges, corners, side profile etc) your interior lights working, your radio and if you have it gps working (gps antenna isn't in the screen - but they have to disconnect it to replace the screen and it often gets missed).