I have purchased a KFH KX3 for my 10.5" pistol. It seemed to be fine for about 30 rounds. Then my ar would not eject shells. The bolt cycles about 1/2 way back. Not enough to eject the shell and insert a new one. Before I got the KFH I had fired 50~100 shots through it and never had this problem.
Is there any trouble hand cycling the bolt? Also try taking the krink back off and see if that fixes it. Have you tried different mags (this is a biggy?) What type of ammo (olympic green tips sometimes causes this), gas system, and buffer are you using?
If you are... and you think that it is causing the gun to short cycle... take it off and see if it solves the problem. I would be surprised if the addition of the KX3 would cause you rifle to short cycle. I suppose that it could. The KX3 could extend the dwell time a bit. What brand and length of barrel are you using? Also, do you know the gas port diameter?