Disturbingly common, according to a NYT investigation. Moreover the machines are often improperly calibrated, software is not available, etc.
https://www.nytimes.com/2019/11/03/business/drunk-driving-br...
https://www.nytimes.com/2019/11/03/business/drunk-driving-br...
The breath test is, I think (I am not a lawyer) insurance that there was reasonable suspicion of the person being drunk, not final proof of anything.