dddd

If a tubing noodle is used under the bottom bracket, it should have a window cut into the bottom at the lowest point, to allow water to drain.

I've worked on a couple of frames with disturbing sharp steps that the cable dragged over, and found thick-walled poly tubing that fit tightly into the guide loop that the cable routes through, such that a minimal length of the tubing could be positioned so as to cross the sharp step feature just behind the loop.

For the standard guides as on the OP's frame, I would run it bare, but would experiment with lubricants while the powdercoat wears down, the thickness of which might be reducing the inside radius of the guide slot, creating a wedging/pinching action on the cable.
GripShift grease is the slipperiest (by far) lube that I've ever used for cables sliding against polymer surfaces.