Leaving The Time Structure Intact?

"The Year of the Ransom."

Manse Everard tells Helen Tamberly that:

"'...the friar Estaban Tanaquil vanished mysteriously two years before, in Cajamarca.'" (p. 669)

(Tanaquil was Steven Tamberly.)

Julio Vasquez tells Everard and Helen Tamberly:

"'Apparently the friar and a soldier went into the house where the hoard was kept one night. When they did not reappear by dawn, the guards grew nervous and opened the door. They were not inside. Every door had been watched. Sensational rumors flew.'" (p. 678)

(A locked room mystery. But a time machine can get in and out of a locked room.)

Vasquez concludes:

"'When I left, the general idea was that sorcerers had been at work. Hysteria was building rapidly. It could have hideous consequences.'" (p. 679)

Everard comments that such consequences:

"'...are not in the history we learned...'" (ibid.)

About another action of the Exaltationist time criminals, Everard reflects:

"We dare not undermine even this forbidden pattern of events." (p. 720)

Yet he later tells Wanda Tamberly:

"'Well, we do have to terminate matters in a way that leaves the time structure intact. We'll put Fray Estaban Tanaquil and Don Luis Castelar in that treasure house in Cajamarca, 1533, a minute or two after the Exaltationists bore them away. They'll exit on foot, and that will be that.'" (p. 732)

When Wanda recalls that the guards became worried, looked inside and found no one and that this generated sensational rumours, Everard replies:

"'...in such cases, when the past has been deformed, the Patrol does annul the events that flow from it. We restore the "original" history, so to speak. As nearly as possible, anyhow.'" (pp. 732-733)

Thus, they annul Vasquez learning that the room had been empty and that sensational rumours flew. Do they also annul Vasquez relaying this information to Everard and Helen Tamberly? I would answer yes because Vasquez relays this information after, not before, the events that he describes.

It seems that Patrol agents know exactly how much they can alter the timeline without causing greater unwanted changes but I do not see where they are able to draw the line.