Can examples be given of the the Ijtihad of the Companions, including our master Ali, may Allah be pleased with them, which contradicted the established authentic Sunnah, along with commentary and explanation?

The Companions possess great virtue and high status, but they are not infallible. They may make mistakes, and therefore, it is obligatory to refer back to the Qur’an and Sunnah when there is a disagreement, as Allah Almighty says: ﴿And if you disagree over anything, refer it to Allah and the Messenger﴾. Their sayings are not authoritative in all circumstances, but their mistakes do not diminish their stature, due to the excuses they may have had, such as the Sunnah not having reached them, or their not believing that the Prophet said it, or their believing it was abrogated, or their independent reasoning (ijtihad) which might have been incorrect. Examples include: Ali burning the apostates before he knew the hadith, "Do not punish with the punishment of Allah," and the completion of prayer during travel by Uthman and Aisha, based on their ijtihad.