Is the rod straight? if you have a bent rod in a straight hole (or a straight rod in a bent hole) it will go in in for a bit and then bind somewhere in the middle.
After inserting the rod in the hole check if it's pressed against one side of the hole. If you turn the rod and it gets pressed against different spots on the edge of the hole as you rotate it thats a good indication the rod is bent or the hole follows a curved path (something that can happen if you're running a delta).
If the rod doesn't need to be held close by the entire hole you could change the geometry of the hole to be the correct size near the openings, but you could widen it out by a bit in the middle where you feel it binding.