According to Spiegel Online, German military(Bundeswehr) has confirmed that the problem lies with trunnion of G36, not with the ammo. With extended use, heat builds up and it weakens the trunnion and polymer contact, resulting in point of impact shift.
Bundeswehr has suspended purchase of additional G36 for the time being. They are considering other solutions, including getting a new rifle to replace G36
H&K has been insisting that the rifle was made within the specification presented by the German military.