Create record with script: weird error U: Validate this value before parsing

Greetings, folks:

All I want is to create the next record:

let nuevoRegistro = {
                'ALUMNOS': [{ "id": regAlumno.id }],
                'ANHO': [{ "id": registroAnho.id }],
                'CENTRO': [{ "id": registroCentro.id }],
                'isAlta': { name: "Yes" },
                'CLASE': { name: clase },
                'CURSO': [{ "id": regCurso.id }],
            };

With the following function:

let crearRegistros = async function (tabla, nuevoReg) {
    return await tabla.createRecordAsync(nuevoReg);
}

And what do I get when I run this? await crearRegistros(tabla, nuevoRegistro);

U: Validate this value before parsing

I couldn´t find any info about scripting errors. I hope someone did and would like to share what I’m doing wrong. Thanks!