https://hadran.org.il/beyond-the-daf/yevamot-53-complicating-yibum-or-chalitzah/
Yevamot 53: Complicating Yibum or Chalitzah - Hadran
When a yavam and a yevama consummate the relationship, that's yibum and now they're married. If they do chalitzah, they're done. But that seems to be only
yevamotcomplicatingyibumchalitzahhadran