odd issue unique field is not working and there is no any error message

Hi all,

I have two content types using unique fields

The first one is PROP:

its fields are:
Title Node module element
URL redirects redirect Redirect module form elements
URL path settings path Path module form elements
Solicitude field_solicitud Node reference Reference from URL
Introduction field_propuesta Long text Text area (multiple rows)
User field_usuario User reference Select list edit delete validate
Price A field_precio_hora_externo Integer Text field edit delete validate
Price B field_precio_hora_interno Integer validate
the second one is REF
its fields are:

Advertiser field_empleado User reference Reference from URL edit delete validate
title Node module element
URL redirects redirect Redirect module form elements
URL path settings path Path module form elements
Phone field_tu_tel_fono Text Text field edit delete validate
date begin and end field_fecha_inicio_trabajo Date Pop-up calendar edit delete validate
Comments field_recomendacion Long text Text area (multiple rows) edit delete validate
voting group_valoraciones fieldset collapsible
required_fields yes
description Valora las siguientes cualdiades del empleado ...

Preparation field_preparaci_n Integer jSlider edit delete validate
Atitude field_atitude_ref Integer jSlider edit delete validate

Well, the problem is odd because when I use unique fields in PROP entity it is working fine, however, if I use Unique Fields in the REF entity it is not working and I don't get any error message.

Some ideas come across to figure the problem out.

Is there any problem between Field Validation and Unique field modules?
Is there any problem between Field Group and Unique Field modules?

Any clue about it?

Thanks heaps
Javier