Oh... I went back and found the pic of your bike.



I had to go back to 2012 to find one on Specialized's site that showed external routing. But some of those models may have carried over to newer model years with lesser tier components.

Is there an access cover that lets you see in the BB shell? I'd expect there to be some way to check and replace the guides, but since I never had a bike with a cable on the inside of the shell, maybe I'm just expecting too much.

I am understanding correctly that the cable goes into the shell and then come out of it running below the chainstay?

It might be some trouble, but I'm wondering about your cable routing under the bar tape. If you detach the cable from the DR and then pull a little slack on the bare cable running along the downtube, then pull on it to put some tension and work your shifter up and down several clicks to see if it's any easier or not. That way you might be able to eliminate the BB guides or stuff on the rear.