Ok, maybe your pins are different. I had a look at a pic of what is probably your model.
Anyway, the bottom line is the pins are not supposed to rotate. If your "keepers" are the little tabs to hold a square cornered pin end, then the nylock nut only has to keep the pin end fully engaged to the tabs.
I wish Kioti would stop cutting corners to compete on price.
My 2013 has quality features all over it, both in design and materials. All of the Kiotis of that era have pins with keepers and a snap ring on the inside. Even if the keeper bolt falls out, the pin will not. This is how pins should be made.
50 cents here, a dollar there, the next thing you know the Kiotis are not the superior Korean brand that they were. If they keep it up that will be the case.
The older CK's were a little mini-ag tractor. Not so much any more.
The NX's are a big step down from the previous DK's and obviously the RX's IMO.
Too much power, not enough weight seems to be the trend.
If your tractor is spinning out before it powers out, then it is not heavy enough, and not balanced. You will just break things...
Rant over and sorry for the sidetrack. Waiting for the dew to come off to cut some more hay. Nothing better to do right now, lol.