After Isamu and Guld, there is a third possibility : the Generals. During the meeting, the Generals were quick to make the investigation as short as possible and everybody was surprised including Glud. Add to the fact Yang said that one of the Generals cleary hated the pilots. And remember everybody that at the beginning of the OAV version right after the battle, one the Generals said that he did not appreciate Isamu's attitude comparing Isamu to a criminal. So as you said, a secret agent employed by the Generals to slow down the projet seems to me possible.