Looks like it’s the Giant then as knowing my luck what you described with the PX frame would no doubt happen to me.
Some Giants have suffered from cracks on the seat tube, but having a Defy 3 Composite myself it’s a lovely bike, but not an all rounder, it won’t take mudguards or a rack, but it’s a very rapid, nice to ride bike, but an aluminium framed bike will be better specified for the same money, Planet X don’t have massive overheads, and aren’t giving loads of bikes to pro’s to race and train on like the big names are, so whilst they do sponsor a junior development team, but it’s not costing an arm and a leg like it is for Trek, Giant, Specialized etc, Planet X have a good reputation for value, as is the Spa I linked to earlier