Honestly its very hard to diagnose something like this without having the knife in hand. The DLC would never cause a binding issue. In fact DLC coatings are actually pretty slick and even though most times they are done over a bead blast finish they will glide like they are mirror polished due to the high hardness and natural lubricity of the finish. Now despite what some seem to think the most friction in a liner or frame lock knife is created by the detent ball riding on the tang of the blade as it rotates. If the lock pressure is too great it will never seem smooth as the ball is digging into the blade too hard increasing friction. I would look at the actual detent ball of your knife. It is likely made of steel. Awhile back I had a few kershaws that had detent balls that had a flat spot and that flat spot was pretty sharp. If somehow that detent ball shifts in its pocket that edge from the flat spot on the detent ball could be essentially cutting a groove into the blade as it moves. Take a folded piece of paper or a pen cap and wedge the liner lock so that the lock is permanently disengaged. If the blade now swings freely you know your problem is either the detent ball, lockbar pressure or both. If however your blade sticks still then that is not the problem.
If we are looking at a problem with the actual pivot I have to ask has this issue always been apparent or did this develop after doing mods? The reason I ask is I see you polished the blade. Did you also do the washers? It would seem some like to take the washers out of the knife and polish them thinking it will make the action smoother and faster. I have found it to actually be the exact opposite. Two things occurs when you sand and polish the washers of a folder and neither of them offer any benefit IMHO. The first is one of increasing friction. If you polish the washers and the blade now you have two glass like materials being pushed together with either oil or grease between them. This creates almost a vacuum between the two surfaces. These two surfaces suction to each other and while yes the surfaces are smoother they grip to each other rather than slip. Also when you polish washers and the blade all the little imperfections that used to carry the lubricant are now gone. In every single knife I have ever polished the washers on it actually made the blade stick rather than slide. The other issue is one of fitment. When you sand and polish washers if you are not using a lap or at the very least rotating the washers as you buff them out you can make them thinner on one side than the other because we as humans are not precision machines. And its very hard to sand something that small with consistent even pressure. If you favor one side of the washer when sanding, you would need to tighten the blade to the point of binding before all blade play is removed because now your washers arent perfectly flat and true. I would look at your washers and your detent ball and see of one of them is causing the issue. Also if you have ever used loctite on your pivot and used to much you can leave a nearly invisible film of the stuff on your parts and it will cause severe binding as well.
