Well, an officer who arrests people for DUI or DUII over and over who are not impaired is wrong and either has not been properly trained or has criminal motives. Either way his city or dept. will pay the price.
My experience is all about Oregon. I am proud to say I have arrested hundreds of people for DUII. That charge has more rules and reports to do it legally and correctly than making any FELONY arrest. I know I arrested many for felonies. By the way it's a lower-level crime than a felony, it's a misdemeanor.
The field sobriety tests are standardized. No officer can administer them in any way that's not listed in the law. Each arrested person has the right to a hearing and be represented by counsel at the hearing. The officer is not represented by anyone at that hearing. They all have the right to a trial by jury or judge.
I never lost a hearing, pretrial motion or a court trial on a DUII case. I had many, nearly all arrested for DUII request a hearing.
Getting intoxicated drivers off the public roads saves lives and should not be taken lightly or done incorrectly.
Of all the cops I worked with, one new guy had arrested about 10 people for DUII that blew .00 or under .08 in just a few weeks. None he arrested were legally drunk or high. He was forced to receive a lot more training with a several other cops. End of his story, he still was unable to know a drunk from a non-drunk and was taken off graveyard patrol and given a daytime position as an investigator. He likely should have been fired. Yes, the PD got at least one lawsuit for false arrest that I remember.
Edit: In that county anyone arrested for DUII and no other evidence of any intoxicates that blew under .08 for an adult under .04 for a comm truck driver or .00 for a minor. The DAs office dismissed the case. Some cases were downgraded to reckless driving if driving was witnessed as reckless.