All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Your question has nothing to do with the Fatwa; it is rather related to research.
In general, what invalidates the marriage according to the Shaafi’i School of jurisprudence is the following:
1- The marriage missing one of its conditions, such as the Wali (guardian) and the witnesses.
2- The marriage including one of the conditions that contradict the objective of the contract, such as when the woman stipulates that the divorce be in her hand, and that she can divorce herself whenever she likes.
3- Setting a time period for the marriage, such as the Mut'ah (temporary) marriage, which is when the man says to a woman who is free from any impediments of marriage: “I will enjoy you for such and such a period.”
4- Pending the marriage, like when one says: If such and such month comes, I will marry my daughter off to you. It is a condition in marriage that it takes effect immediately.
5- When the woman has one of the impediments of marriage, such as the waiting period; it is not valid to marry a woman who is observing a waiting period from another marriage [after being divorced] because the waiting period is obligatory in order to preserve the family lineage.
These are some of the matters that invalidate marriage according to the Shaafi’i School of jurisprudence; by research, you may find other matters that invalidate the marriage.
Allah knows best.