Whyte T130 internal seatpost clamp issue

Hi just wondering if anyone else has experienced this.

just replacing dropper cable on alloy T130 and upon retightening the bolt for the internal mechanism as it gets tighter but not upto torque the bolt is clicking (snapping sound) upon tightening. The sort of sound that makes you stop and not want to continue. I’ve unscrewed it and cleaned it but the same each time, bolt looks fine. 

How is it best to treat these please? Did try putting assembly compound on the bolt but still does it. Any suggestions or experience welcome.