As fine as the King James Version of the Holy Bible is--and its style and sonority are indeed hard to beat, there are also many other fine translations today which provide us with alternate readings, which though perhaps not as dignified sounding as the venerable KJV, can to their credit open up new vistas of understanding for us. Since most translations are the result of a concerted effort of many biblical scholars who are well versed in the original languages in which the Bible was written, we are not well versed can take comfort in the proverb, "In the multitude of counselors there is safety" (11:14; 24:6).
Granted, the element of bias or the issue of blind spots can never be eliminated entirely, even among a multitude of translators. I suggest, however, the vast majority of Bible translators are men and women of good will who are interested in translating God's word faithfully, accurately, and consistently according to their respective and often different mandates. Think of their mandates as their mission as to the kind of translation they are after, whether a word-for-word translation, a freer thought-for-thought translation (or even paraphrase), an accurate translation, an easy-to-understand translation, or any combination of the above criteria and more.
The verse that is central to your question may in the King James Version seem patently "unfair," but it begins to sound a little less so as we compare Leviticus 19:20 and the two verses that follow it side-by-side with numerous other versions, as is possible with a website such as biblestudytools.com. When we do so we begin to see a pattern emerge such that certain group of translations translate the verse quite similarly, with very few major differences among and between them, whereas another group of translations tend to translate the verse quite dissimilarly vis a vis the first group. Occasionally, even, a translation sticks out like a beard in a nursery for newborns because it translates a verse in a way that resembles neither the first group's nor the second group's but seemingly strikes out on its own! What to do, what to do . . .?
Some Bible readers find this situation appalling, and instead of considering each translation to have something of value to offer, they will "stick to" one version exclusively so as not to have to deal with alternate readings, which they find confusing and upsetting. Some churches even have an unwritten rule that Bible version X is the only version to be read in their churches, which to me seems a bit extreme, since there are very good reasons why various versions of the Bible are different. Moreover, these differences can often shed light on the meaning of a given verse, which is not only a good thing but is also good hermeneutics.
Another good thing is to read a verse in context, to make sure we are not missing a meaning or misunderstanding it by having tunnel vision. When we consider Leviticus 19, for example, we are only helped when we know that it has been described as
"the highest development of ethics in the Old Testament, [which] . . . perhaps better than any other in the Bible, explains what it meant for Israel to be a holy nation (Exod 19:6). The chapter stresses the interactive connection between responsibility to one’s fellow man and religious piety, the two dimensions of life that were never meant to be separated."
In other words, the chapter is all about fairness and evenhandedness. In interpreting one verse, then, we need to consider it in the context of what comes before and what comes after, which will often consist of an entire chapter and/or the entire book, or even the entire Bible, which is called the analogy of Scripture. By conflating all the different permutations found in many versions, you end up with something like this, which could be described as a sort of amplified version:
"If a woman who is a bondslave, or servant, to a recognized master, and the maid is engaged to another man who intends to buy her and thus give her her freedom within his household as a second wife or concubine (even if she is a former noble woman of kin who has fallen on hard times), and she has unforced and consensual sexual intercourse with her master, then
this is how the situation should be handled: after there is an investigation and an inquiry which uncovers all the facts, both of them shall be punished, she by being scourged and he by paying a fine to the prospective owner of the maid, since she has been an equal and willing partner in the sin, and since he by defiling her has devalued her to her betrothed. Neither of them should be put to death, however, because there is a distinction between a master having sex with a betrothed slave girl and a master who seduces a married woman who has either been given her freedom or was never a slave to begin with. The former is a sin and requires a guilt offering; the latter is adultery and is punishable by death."
As you can tell, no self-respecting Bible translator would translate this verse--or any verse, for that matter--in this way. First, the Bible would be four times longer than it is currently. Second, different translations are often based on different source documents and manuscripts, and for consistency's sake, translators tend to stick to certain families of texts when translating. In other words, "they puts in their nickel and takes their choice." Translation: there are two or more ways of saying essentially the same thing, so there's nothing inherently wrong about sticking to one way and ignoring another way--perhaps even an equally legitimate way--of saying it.
In looking at the verses in question, if it clear both the master and the maid are punished, albeit in different ways: she by being scourged, and he by paying a fine to the aggrieved fiancé and offering a sacrifice (a ram) at temple, where the priest will make atonement for him.
Is this fair, you ask? Yes. How better to make the master pay for his offense than by hitting him where it hurts the most: in the pocketbook. How better to get the maid to remember the seriousness of her offense than by experiencing some physical pain. Keep in mind, however, some Bible versions have both of them being scourged, while some have neither of them being scourged with only the man being required to atone for and be forgiven of his sin by offering a blood sacrifice through the priest at the temple.
In conclusion, my purpose here is neither to suggest which version of Leviticus 19:20 (again, vv.20-22) is the best, nor which criteria should be used in determining which version is best. Rather, I simply encourage you to keep in mind that virtually every Bible version has something worthwhile to offer. When you next read something in the Bible that seems unfair or that triggers a question in your mind, consult several versions and several commentaries. By doing so, not only will many, if not most, of your questions be answered and those apparent contradictions be explained, but your confidence in the Bible's reliability will soar.