I seem to remember troubleshooting one once. Seemed like the best solution was to replace with the nearly equivalent Siemens one, which did have the advantage over the Rockwell of using all metric threads and bearings, plus alignment was easier, you did not need the slings, chain blocks and sledge hammers required for the Rockwell, this was easy to do with only a percussion drill, some 32mm bits and some minor adjustment with nitrogen tetroxide and 93 percent hydrogen peroxide.