Mal 3:6, For I am the Lord, I change not. Rev 22:19, And if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.
It is changes to the English language that modifies the KJV. Not any one person. It is 400 years old. Therefore has many issues due to the changing language and other reasons.
For example, because of the changes in the English language, a number of words occur in the King James that make zero sense to most people today. These include the following nuggets that you will find scattered here and there:
Almug
Algum
Charashim
Chode
Cracknels
Gat
Habergeon
Hosen
Kab
Ligure
Neesed
Nusings
Ouches
ring-straked
sycamyne
trow
wimples, ….
The King James translators also translated some animal names into animals that in fact we now have pretty good reason for thinking don’t actually exist:
unicorn (Deut. 33:17)
satyr (Isa 13:21);
dragon (Deut 32:33) (for serpent)
cockatrice (Iswa 11:8),
arrowsnake (Gen 49:11, in the margin).
Moreover,, there are phrases that simply don’t make sense any more to modern readers: Phrases that no longer make sense:
ouches of gold (Exod. 28:11);
collops of fat (Job 15:25);
naughty figs (Jer 24:2);
ien with (Jer. 3:2);
the ground is chapt (Jer 14:4);
brazen wall” (Jer 15:20);
rentest thy face (Jer. 4:30);
urrain of the cattle (Exod. 9:2);
And there are whole sentences that are confusing at best, virtually indecipherable (or humorous)
And Jacob sod pottage (Gen 25:29)
And Mt. Sinai was altogether on a smoke (Exoc. 19:18)
Thou shalt destroy them that speak leasing (Ps. 5:6)
I trow not (Luke 17:9)
We do you to wit of the grace of God (2 Cor. 8:1)
Ye are not straitened in us, but ye are straitened in your own bowels (2 Cor. 6:12)
He who letteth will let (2 Thes 2:7)
The words of the wise are as goads, and as nails fastened by the masters of assemblies, which are given from one shepherd (Eccles. 12:11)
Other sentences make sense, but would today be considered somewhat problematic – at least for the sacred Scripture. My favorite is the one that refers to a man who: “Pisseth against the wall:…. 1 Sam 25:22, 34, I Kings 14:10!