And it does something worse than that

Checking does not only fail to settle the doubt. It wears away the very thing you were checking with.

Researchers had people check a set of gas hobs over and over. Their memory did not get more accurate. Their confidence in their memory fell, and the memory itself became less vivid and less detailed the more they checked.

Read that twice, because it is the whole mechanism. The more carefully you check, the less you trust what you saw. Which makes you check.