There could be a few reasons. If your gorditas fell apart, it's possible the masa dough was too dry or lacked enough binding. Try adding a splash of oil. Be sure you use the right amount of water and knead the dough to the right consistency. Additionally, letting the dough rest for a bit covered with a kitchen towel before shaping can also improve its texture and prevent breaking. Finally, your filling might be too juicy causing your little dough pocket to fall apart.