crack under pressure

crack under pressure (reveal information that one normally would not reveal) — расколоться, просыпаться; разболтать || срываться; испытывать нервный срыв

Example 1: Criminals crack under pressure when law enforcement officials need information. (David W. Miller)

Example 2: Prisoners of war often crack under pressure.(David W. Miller)

Example 3: I don't expect a lot from the babies, because they sometimes crack under pressure, like today.

see also
[spill one's guts]

[crack up]