Does a condition lapse due to forgetfulness absolutely, or in specific cases, such as mentioning God's name when slaughtering an animal?

The Basmala (mentioning the name of Allah) is obligatory during slaughter (dhakat) provided one remembers and is capable, according to the Maliki and Hanafi schools, and it is the well-known opinion among the Hanbalis. However, it is not obligatory according to the Shafi'i school. Sheikh Muhammad ibn Salih al-Uthaymin holds the view that the Basmala is a condition for the validity of the slaughter and it is not waived whether done intentionally, out of forgetfulness, or out of ignorance, due to the generality of Allah's saying: {And do not eat of that upon which the name of Allah has not been mentioned} (Quran 6:121). Scholars have differed on this issue, with some opinions stating: that it is a Sunnah (recommended) and not obligatory, or that it is obligatory but waived by forgetfulness and ignorance, or that it is a condition for the slaughtered animal and is waived by forgetfulness, while it is not waived in the case of hunting.