Django order_by not working properly

Question

I'm trying to get all the conversations ordered by it last message, but when I use the order_by clausule, the conversations are repeated.

Query without order_by:

conversaciones = Conversacion.objects.filter(usuarios=request.user)

Result (Grouped by Conversations but not ordered by the most recent last message first):

Query with order_by:

conversaciones = Conversacion.objects.filter(usuarios=request.user).order_by('-mensaje__fechaEnvio')

Result:

My models.py:

class Mensaje(models.Model):
    remitente = models.ForeignKey('Usuario', on_delete=models.CASCADE, related_name='remitente')
    destinatario = models.ForeignKey('Usuario', on_delete=models.CASCADE, related_name='destinatario')
    cuerpo = models.TextField(validators=[MaxLengthValidator(750)]) 
    leido = models.BooleanField(default=False)
    fechaEnvio = models.DateTimeField(auto_now_add=True)
    conversacion = models.ForeignKey('Conversacion', on_delete=models.CASCADE)

    class Meta:
        ordering = ['-fechaEnvio'] 

    def __str__(self):
        return str(self.remitente) + ' -> ' + str(self.destinatario)


class Conversacion(models.Model):
    usuarios = models.ManyToManyField('Usuario', related_name='usuarios')
    agresion = models.ForeignKey('Agresion', on_delete=models.CASCADE)

    @property
    def ultimoMensaje(self):
        return self.mensaje_set.latest('fechaEnvio')

Answer 1

I found a solution:

conversaciones = Conversacion.objects.filter(usuarios=request.user).annotate(max_fecha=Max('mensaje__fechaEnvio')).order_by('-max_fecha')

I'm using MySQL so I can't use distinct with params.

Answer 2

As @jota suggested, I can add something in your model Mesanje. Make ordering a tuple and don't forget to add a comma and don't forget to make migrations again.

class Mesanje(models.Model):
      ........
      class Meta:
           ordering = ('-fechaEnvio',)