I have a several thousand nested keywords. I often use nesting to organize them further. As my keyword lists have grown, there seems to be a bug that prevents me from using drag and drop to reorganize them. Near the top of the list, I can use drag and drop. However, near the bottom of the list, Drag and drop stops working and instead a large set of keywords gets highlighted instead without being able to drag and drop. This bug has been around since at least Lightroom 4, was present in Lightroom 5, and is also present in Lightroom CC.