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