So, what I'm about to say must come with a significant caveat: I'm not a specialist in witch history, and only really know about witchcraft in the Holy Roman Empire. Regional variation was massive; in some areas (e.g., Normandy, if I recall correctly), men were prosecuted more than women! What I'm saying here goes strictly for only what I say, though my impression is that these observations are broadly representative.

What must be remembered when talking about witchcraft is that while it may seem "irrational" from our viewpoint - which is so much more "modern" and "rational"! ...well, sometimes - most early modern people sincerely believed in witchcraft. They saw maleficent magical power as a genuine threat, and wanted to make sure that they took out that threat. Wouldn't you? Belief in magical maleficence is pretty common worldwide, after all.^(1) But they also believed in justice, and (generally) believed that they could be wrong.

Mild content warning for the next paragraph.

In 1527, one Margareth Los, an inhabitant of the Duchy of Württemberg, was accused of witchcraft. After being whisked away in the streets, she was brutally tortured; I won't go into the graphic details, but her account is translated in full in the paper I cite below. It was so bad, it seems her perception of time was completely thrown out of joint (consistent with modern understandings of the psychological impact of extreme physical torture). While the details are unclear, it seems she was tortured for days, if not weeks, on end. But she never confessed. As a result, she was locked up for three and a half years, and then expelled from the Duchy. However, she was never prosecuted for witchcraft.^(2)

As a result, she couldn't be prosecuted, since there was no other evidence to go on. The rule of law mattered even in witchcraft trials, something that can be seen in other examples (as that of Elizabeth Lorenz), even if not all the time.^(3) Lots of educated legal commentators were actively worried about how popular prejudice and fear could produce over-hasty judgements, and made sure that they influenced trials against this. In fact, Los actually launched a legal complaint about her treatment, and her torturer, Jakob Furderer (unfortunate name; I'm reminded of Hannibal Lecter), was criticized for his conduct in court. However, she didn't manage to secure more than some compensation for her properties that were sold whilst she was imprisoned.^(4) Even so, the point stands: not only was she not convicted, she managed to get a little bit of justice for her mistreatment.

More powerful people generally had recourse to better methods. Katharina, mother of the famous astronomer Johannes Kepler, was prosecuted for witchcraft in the 1620s, and he made sure to use all of the considerable intellectual and political friendships and favours he had to get her off. Unsurprisingly, he was successful.^(5) However, it wasn't always so easy. In the ecclesiastical principality of Bamberg in the late 1620s, one Dorothea Flockh was imprisoned and tried for witchcraft. She and her family were very well-connected indeed: they appealed first to regional authorities and powers, and then to the Emperor himself, Ferdinand II. However, even the Emperor ordering the Prince-Bishop to release her and stop the trial (so it could be conducted fairly in Vienna) couldn't save her, and in 1630, she was executed. Her newborn baby (she gave birth in captivity) was ripped from her arms moments before she was decapitated.^(6)

This caused massive outrage. Of course, part of that was because an Imperial prince had defied the orders of the Emperor himself, multiple times. However, a lot of it was because this was widely viewed as a perversion of justice. Witchfinders were expected to find innocent people innocent, and Flockh was widely perceived as an innocent woman - or at least one who hadn't properly been found guilty. That she had just given birth and was torn from her child before being judicially murdered just added to the tragedy, especially for the many powerful people who knew (or knew of) her.

So, yes, in answer to your question, witchfinders did find people innocent. In some places, they did it quite a lot; I believe overall across Europe, "only" 50% of those accused of witchcraft went to the stake.^(7) In some areas, this number was quite a bit higher, and it was certainly expected that anyone who was genuinely innocent would be let go - though it might well take torture to establish "genuine innocence". The witch trials were in many regards horrific, but it would be a mistake to regard them as wholly mindless exercises in random violence.

References

^(1) Ronald Hutton, “Anthropological and Historical Approaches to Witchcraft: Potential for a New Collaboration?” in Historical Journal 47 (2004), 413-434.

^(2) Daniel Jütte, “Survivors of Witch Trials and the Quest for Justice in Early Modern Germany” in The Journal of Medieval and Early Modern Studies 50 (2020), 349-375.

^(3) Peter A. Morton (ed.), The Bedevilment of Elizabeth Lorentz, trans. Barbara Dähms. Toronto: University of Toronto Press (2008); cf. William Bradford Smith, “Friedrich Förner, the Catholic Reformation, and Witch-Hunting in Bamberg” in The Sixteenth Century Journal XXXVI (2005), 115-128.

^(4) Jütte, “Survivors of Witch Trials“.

^(5) Ibid.

^(6) William Bradford Smith, Reformation and the German Territorial State: Upper Franconia, 1300–1630. Woodbridge: Boydell & Brewer Limited (2008).

^(7) Malcolm Gaskill, Witchcraft: A Very Short Introduction. Oxford: Oxford University Press (2010).

This answer from 2018 by u/Surprise_Institoris points to at least one case of what you ask about!

(Edit: misspelled username)

I'm not sure what you mean by "witchfinder", but I have some expertise relating to witch trials. I have done some research on superstitions and supernatural events in late medieval and early modern Europe, this included witch trials. My expertise is mostly limited to this region and time period though, I can not speak on others. However, typical depictions of witch trials in Western media are mostly based upon popular ideas of medieval Europe, so I assume that its relevant expertise. Within the context I studied, I can say that it most definitely happened to have accused witches who entered a trial go free. This in fact happened all the time. While the numbers and information we have isn't ironclad and is very regionally specific, it's still safe to say that many - if not most - of those who entered a witch trial were ultimately not executed.

The way witch trials are depicted in Western modern media really isn't historically accurate at all. These depictions will often show a very dramatic group of townspeople already having made up their mind and employing some very drastic "tests" to reaffirm something that was already predetermined, namely the guilt of the accused. While there are differences depending on the region and time period, most witch trials weren't nearly that dramatic. Popular Western media tends to also show townspeople calling for a witch trial as if it's a daily occurrence. They weren't. Witch trials were ultimately fairly rare. While originally historians estimated several hundred thousands of casualties between the late medieval and early modern time periods, this number has been steadily declining these past decades as the direct result of more research. Most recent articles I've read estimate about 30.000 casualties. While that may seem like a big number, this is for most of Europe and spanning several centuries. With that in mind, we can safely conclude that witch trials most certainly weren't a common occurrence - let alone witch executions.

What's more, those dramatic depictions of drastic "tests" or instant executions based upon preconceived notions of guilt are also fiction. Those involved usually did in fact try to genuinely figure out whether someone was a witch or not. This may seem entirely crazy to us, but it's important to remember that their worldview and way of thinking was vastly different from ours. They reasoned with different concepts, ideas and they saw the world very differently. While their superstitions and beliefs are often very confusing to our modern perspective, they were a part of a coherent worldview and the reasoning behind it all wasn't entirely random or haphazard. There was a certain rhyme and reason to their worldview and how they employed this during those trials. This to me as a historian is easily one of the most difficult things to explain to someone who hasn't extensively studied history. How do you describe the mind of the average medieval European? It's a a seemingly insurmountable task because trying to think like someone else in itself is already an insanely difficult and imperfect exercise. It's only through extensive research and practice that I started to see glimpses of the mind and worldview of the average medieval European. It's all very alien, but like I said before it's also in a way... coherent?

So we've determined that unlike the depictions in popular Western media, witch trials were fairly rare and also mostly tried to follow a certain genuine - albeit alien - logic. What remains are the methods employed. Again, not nearly as dramatic as those popular depictions would have you believe. Most witch trials came down to character witnesses and personal testimony. The accused would often have people speak on their behalf. The more respectable their character witness, the more weight their testimony held. The accused would often also speak in an attempt to defend themselves from the accusations. What this means is that those who were the most vulnerable to being subjected to a witch trial and most likely to be found guilty were those already partially ostracized by the community, be it due to mental/physical illness or other factors that had alienated them from the local population. Those who could also not adequately speak for themselves were even more at risk.

Don't get me wrong, this was a vicious practice and at times guilt was predetermined. There are also some notable trials that were highly dramatic. Still, the popular depiction in Western media of witch trials generally is a far cry from how and how often they presented themselves within Europe in the late medieval and early modern time period.