[timtammittee]

In the Frontex Western Balkans Annual Risk Analysis 2016 Frontex investigated Nationality swapping and they found:

"In 2015, 173 042 migrants who claimed Syrian nationality were screened; of which 85.8% were assumed by screeners to be Syrian nationals. As regards the rest, 8.6% were assumed to be Iraqi; 2.5% Palestinian, 1% Moroccan, and 2.1% were assumed to be of other nationality."

So yes, 14.2% of the people who claimed to be from Syria really originated somewhere else. But, if we again sum up those who come from a country who is currently in a state of conflict (I included Palestine), we gain 97%.

Edit: Also, you should note that people are screened again during the process of applying for asylum. So I guess the number of wrongly assigned nationalities is neglectable.