As for the 12er Shia fiqh we have contradictions such as Muta being conditional marriage or a Sunnah. Which one is it?
From Risalat Al Mutah by Sh. Mufid,
And by this isnad from Ahmad b. Muhammad from Musa b. `Ali b. Muhammad al-Hamdani from a man he named from Abu `Abdillah عليه السلام. He said: There is not a man who does mut`a then does ghusl but that Allah creates from every drop (of water) that drops from him seventy angels who seek forgiveness for him until the day of the resurrection, and who curse the avoider of it until the Hour rises. And this is but a little of a lot in this meaning
One must also be careful when doing it as there are also narrations which state that one should not do it if they are needless of it, such as,
Muhammad b. Ya`qub from `Ali b. Ibrahim from his father from Ibn Abi `Umayr from `Ali b. Yaqtin. He said: I asked Abu ‘l-Hasan عليه السلام about mut`a. So he said: What do you have to do with that when Allah has made you needless of it.
And in another narration, the Imam speaks of the need to preserve the image of the Shia,
And from them from Sahl from `Ali b. Asbat and Muhammad b. al-Husayn all from al-Hakam b. Miskeen from `Ammar. He said: Abu `Abdillah عليه السلام said to me and Sulayman b. Khalid: I have forbidden mut`a upon you two by me so long as you remain in Madina, for you have increased your entering in upon me and I fear that they take you and it be said: These are the companions of Ja`far
Both narrations from Wasail Shia under the chapter, "Dislike of mut`a when one is free of need from it and it involves abomination or the corruption of the women"