I would not prefer saying that EU is shaking but it is obvious that it is in the middle of a serious crisis. As it is known, some EU countries opened the borders for refugees mostly from Syria and Iraq who have been escaping from ISIS and are seeking for asylum. That was the moment when the disagreements between the members of EU appeared.
Different views on the distribution of the migrant influx has led to the disagreement between Western and Eastern European countries. Based on their distinct 'infrastructure', while the policy of the West specially Germany's have been more welcoming, the East have been trying to be much more cautious about the influx. Thus, EU members have had difficulties to compromise which has not brought any solution but has provoked the bigger problem within EU.
The problem of limiting the Schengen zone! This is the moment when EU has faced a bigger crisis. The idea emerged after the Paris attack whose perpetrators were ISIS members and most importantly one of the attackers had come to Europe as an aslylum seeker. So, it was not suprising that there would be some ideas among EU members concerning increasement of the controls in the borders. However, it was not expected limiting the free movement deal which would affect the citizens of other European countries as well - Southerns and Easterns particularly. I believe that was when many people started to think about the failure of EU.
Frankly, it was an idea which poped out after the attack that was 'shocking' for Europe. Nevertheless, European Union would not accept such an idea as it is aware of the possible consequences that might face all the member countries. That's why, the Union would not let such an idea realize as it might prompt the worse; the 'falling' of the Union. Instead, it is highly feasible that the European Union will come up with other policies which may not solve the problems soon but will not allow other crisis that would harm the Union.
PS: EU has just announced 3 billion euros aid for the Syrian refugees in Turkey so that they would live in better conditions thereby will not attempt to go Europe. It seems that EU carry outs its own 'methods' to prevent any crisis that would entail to a failure.