Are we sinful for performing the Hajj obligation outside official working hours, given the hospital's circular prohibiting Hajj, knowing that we perform our work perfectly?

Hajj is immediately obligatory according to the majority of scholars, based on evidence including the Prophet's (peace be upon him) saying: "Perform Hajj before you are unable to perform it," and "Hasten to Hajj – meaning the obligatory one – for none of you knows what might befall him." So, whoever is able to perform Hajj without disrupting their work, it becomes immediately obligatory upon them. Otherwise, resignation becomes obligatory to fulfill the obligation.