It should be possible to check for corruption in the process by having the AGI not use some known information in the reconstruction, then asking the reconstruct to answer questions with known answers.

(For example, the AGI could not use the (known, from records) birthdate of the person during reconstruction; afterwards, if the reconstruct doesn't remember their correct birthdate, that would be strong evidence that the process had failed. Given a sufficiently large number of these tests, the superintelligence could verify with reasonable accuracy the fidelity of the reconstruction.)