What must be done to rectify a corrupted Umrah when the obligatory Hajj is approaching, and what are the consequences of transgressions committed out of ignorance?

Umrah is not invalidated except by certainty of circumambulating (Tawaf) while in a state of major ritual impurity (Janabah) after the emission of semen necessitating a ritual bath (Ghusl). Doubt, however, does not invalidate it. If you are certain of Janabah, then the Umrah is not valid, and it is necessary to cease the prohibitions of Ihram and go to Mecca to re-perform the Tawaf and Sa'i based on the previous Ihram. As for prohibitions committed due to ignorance, nothing is required for them unless they are of the nature of destruction (like cutting hair or nails), in which case the expiation of choice (Fidyah al-Takhyir) becomes necessary.