This doesn't prove my point, but manufacturers do aggressively fight against researchers identifying flaws in their products. Given the high stakes (+ the fact this isn't a security issue, really), it seems like a major smell to me.
There are reports out there of people convicted, who are blocked from examining the devices used as the primary piece of evidence against them.
Also, after years of effort to discredit breathalyzer results, convictions ARE being overturned regularly.
NJ overturns > 27k convictions because of breathalyzer issues - https://www.nytimes.com/2018/11/13/nyregion/nj-dwi-convictio...
MS judge suspends admission of breathalyzer evidence -- https://www.bostonherald.com/2019/01/10/breathalyzers-tempor...
More relevant info - https://www.zdnet.com/article/draeger-breathalyzer-breath-te...
No idea how rampant this is, every system will have flaws. But I question whether we can use the alcohol breathalyzer example without acknowledging there are significant unanswered questions w/r/t accuracy.