You did not say what model this is on.
This question is somewhat subjective because it could be one of several situations.
If the cable housing is in good shape and not kinked anywhere, simply lubricating the cable with cable ease could very well solve the problem. If ignored I would expect the cable to eventually break.
It also could be that the cable housing is damaged to the point that there is a sharp edge somewhere cutting the cable.
If you're having the work done in a shop, and they already are taking out the cluster, it would be a good time to replace it. If it is a 123 series car, getting the cluster out is such a simple job, it may not make much difference in cost anyway.
You are on the right track though. I feel quite sure that the cable is causing the problem you describe.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in