Sheikh Yahya explains the weakness of the phrase "(وشاهدين / وشاهدي عدل)" in the hadith.

((لا نكاح إلا بولي وشاهدي عدل)) ‟There is no valid marriage except with a guardian and two just witnesses.” CONCLUSION: This hadith has been narrated by a group of companions and is considered authentic. However, the addition of "and two just witnesses" is transmitted through chains that contain severe weakness. None of the chains are reliable; whether individually or collectively.