Here's an article:
https://news.vice.com/article/the-us-keeps-mistakenly-deporting-its-own-citizens
A couple of notes: looks like that report was in 2011, so who knows how much more in the last 5 years. Published by a researcher at Northwestern U. I have not read any of the research, and while globally have some qualifications in assessing research studies, I wouldn't really trust my ability to critique this kind.
Nonetheless, it is published from research from a reputable source. Even if the number is significantly off, the estimate to me credibly represents a magnitude of failure that is far beyond my comfort.