ShanesBigSanityCheckTestCase.testScenario1 is failing sometimes

In my environment, the unit test ShanesBigSanityCheckTestCase.testScenario1 is sometimes failing (It's passing successfully in around 75% of cases, but in 25% cases it's failing).

In case that the failure occurs, it happens on line 159 in statement:

        assert !em.createQuery(
                "select a from IdentityObjectAttribute a where a.identity.id = :id and a.attributeName = :attributeName",
                IdentityObjectAttribute.class)
            .setParameter("id", u.getId())
            .setParameter("attributeName", "profilePhoto")
            .getResultList().isEmpty();

which is failing because resultList is sometimes empty.

Still not sure about the cause of this. I wonder if it's just me or if it happens for someone else as well. I've reproduced with Ubuntu 12.10, Oracle JDK 1.6