he believes a manager crosses the threshold into entrepreneurship when “the exercise of his/her judgment is prone to error and s/he bears responsibility for its correctness.”

It looks like your query is incomplete, but you seem to be asking about the idea that a manager crosses into entrepreneurship when their exercise of judgment is prone to error and … something else. This concept is often linked to the economist Israel Kirzner or Joseph Schumpeter, but more precisely, it resembles the idea expressed by economist Frank Knight, who distinguished between the roles of managers and entrepreneurs based on uncertainty and judgment. A fuller version of the idea might be: A manager crosses the threshold into entrepreneurship when "the exercise of his/her judgment is prone to error and the outcomes are uncertain," meaning the entrepreneur makes decisions in situations where outcomes are not predictable and risk cannot be fully calculated. In contrast, managers typically operate in situations of risk that can be measured and managed. If you want, I can help you find the exact quote or elaborate on the concept! Could you provide the rest of the sentence or any more context?