The number of properties in the Dependent and Principal Roles in a relationship constraint must be identical.

Hello everyone!
I would like your help in a project I am developing for a free flight school ...

I'm working with WEB API 2 with EF6

I was able to write a good part of the code but now I have this exception:

One or more validation errors were detected during model generation:

Aula_Agenda_Target_Aula_Agenda_Source: : The number of properties in the Dependent and Principal Roles in a relationship constraint must be identical.

My Aula Class:

public class Aula
    {
        public Aula()
        {
        }

        //Primary Key
        public int AulaID { get; set; }

        //Fields
        public int UsuarioID { get; set; }
        public int AgendaID { get; set; }
        public DateTime Entrada { get; set; }
        public DateTime Saida { get; set; }

        //Virtual Properties
        public virtual Usuario Usuario { get; set; }
        public virtual Agenda Agenda { get; set; }
    }

My Agenda Class:

       public Agenda()
        {
            Aulas = new List<Aula>();
        }
        // Primary Key
        public int? AgendaID { get; set; }


        // Fields
        public int CursoID { get; set; }
        public int UsuarioID { get; set; }
        public int EnderecoID { get; set; }
        public string Descricao { get; set; }
        public DateTime? Inicio { get; set; }
        public DateTime? Termino { get; set; }
        
        public Curso Curso { get; set; }
        public Usuario Usuario { get; set; }
        public Endereco Endereco { get; set; }
        public virtual ICollection<Aula> Aulas { get; set; }
    }

My Aula MAP:

    public class AulaMap : EntityTypeConfiguration<Aula>
    {
        public AulaMap()
        {
            // Primary Key
            this.HasKey(k => new { k.AulaID, k.UsuarioID, k.AgendaID });

            // Properties

            // Table & Collumn Mappings
            this.ToTable("Aula");
            this.Property(u => u.AulaID).HasColumnName("AulaID");
            this.Property(u => u.AgendaID).HasColumnName("AgendaID");
            this.Property(u => u.UsuarioID).HasColumnName("UsuarioID");
            this.Property(u => u.Entrada).HasColumnName("Entrada");
            this.Property(u => u.Saida).HasColumnName("Saida");


            // Relationships
            this.HasRequired(r => r.Usuario).WithMany(d => d.Aulas).HasForeignKey(fk => fk.UsuarioID);
            this.HasRequired(r => r.Agenda).WithMany(d => d.Aulas).HasForeignKey(fk => fk.AgendaID);
        }
    }

My DbDiagram:
https://github.com/dicataldisky/DACSistemas.Central-de-Cursos.BackEnd/blob/master/DBDiagram.pdf

My Project on GITHUB:
https://github.com/dicataldisky/DACSistemas.Central-de-Cursos.BackEnd


Please Help Me!