@Gali Badner: Thanks. Simple as that. After removal of @AttributeOverrides all tests on my site are passed as before the version update.

@Vlad Mihalcea: i see your point. the @AttributeOverrides was present since usage of hibernate 4.x.x and was made by a generator more than 3 years ago. as far as i remembered there was a time when it was not working without the presence of this line. But anyway, i'm even happier without it =)

Thank you both for your very appreciated inputs,
T