@kjgrf thank you for sharing this information. I tried with the steps you provided above to label all the electrodes with the data you had shared earlier and it works fine. Can you maybe share few of the data which is creating the issue to better debug it at our end here ?
Also if you could try one more thing. For the data creating issue, try regenerating the isoSurface by right clicking on CT > CT segmentation > Generate thresholded mesh from CT. This should not affect any of the implantation already done rather just regenerate a fresh isoSurface mesh to work on. They try following the steps you mentioned above and see if it still gives any error.