EF6 many to many duplicate column - entity-framework

Question

I got a database first many to many between
UsagerEW <> PermissionsUsagerEW <> Permissions
I manually add the Many2Many relation:
modelBuilder.Entity<PermissionUsagerEW>().HasKey(k => k.id);
modelBuilder.Entity<UsagerEW>()
.HasMany(u => u.Permissions)
.WithMany(p => p.UsagerEWs)
.UsingEntity<PermissionUsagerEW>(
p => p.HasOne(e => e.permission)
.WithMany()
.HasForeignKey(e => e.permissionId),
p => p.HasOne(p => p.usagerEWcode_intNavigation)
.WithMany()
.HasForeignKey(e => e.usagerEWcode_int)
);
The midle table EF generate:
public partial class PermissionUsagerEW
{
public int id { get; set; }
public int permissionId { get; set; }
public int usagerEWcode_int { get; set; }
public virtual Permission permission { get; set; }
public virtual UsagerEW usagerEWcode_intNavigation { get; set; }
}
It’s an old database and some table do not have an id as FK and got code_int instead.
Everything works well except when I try to add permission to one user.
I try updating directly the PermissionsUsagerEW (middle table) or by the navigation properties of the user table.
In each case I got this error:
The column name 'permissionId' is specified more than once in the SET clause or column list of an INSERT.
When I look in the generated SQL code, I see that the 2 fields are duplicate with the same name but starting with a capital letter:
SET NOCOUNT ON;
INSERT INTO [PermissionUsagerEW] ([Permissionid], [UsagerEWcode_int], [permissionId], [usagerEWcode_int])
VALUES (#p0, #p1, #p2, #p3);
SELECT [id]
FROM [PermissionUsagerEW]
WHERE ##ROWCOUNT = 1 AND [id] = scope_identity();
Any idea?