To clarify, a mistake is an error which causes the tests to be invalidated. Theranos had to throw out all Edison test results for 2014 and 2015. Clinical decisions were made as a result of these tests and it is not unreasonable to believe that patients may have been harmed as a result of faulty information. This would be the equivalent of a plane crash for an airliner.

False positives and false negatives will occur with all testing and there are protocols in place to detect false readings. While most tests are accurate, an inaccurate result is not considered a mistake since the tests themselves are not perfect. (Given that you followed proper procedure)

Most blood tests are imperfect by nature (specificity and sensitivity are almost never equal to one). No need to point out a specific and very questionable example.