Since upgrading to High Sierra recently I've run into several bugs, but this one has been the most annoying. I will use the report format suggested by joemikeb to explain:
macOS High Sierra 10.13.6, specifically the Finder
SUMMARY OF PROBLEM:
Reordering of items under Devices in the sidebar of Finder windows gives unexpected and undesired results, including duplicated names.
Always reproducible, rebooting fixes it, quitting and relaunching the Finder does not.
DETAILED STEPS TO REPRODUCE:
Reorder the icons of mounted hard drives/partitions up or down in the Devices list. It helps to have at least 4 items showing for the problem to be evident.
Items should retain their accurate names and positions no matter where they are moved in the list.
As I move the icons up or down, the icons will be renamed to be a duplicate of another item already listed, and/or icons will move back to their original locations. For example, if I start with this and try to move Macintosh HD down to put it under Backup One:
I may end up with this:
On my system, I noticed the problem only occurs with my startup drive and the two clone backup drives I have (a nightly and a weekly) of the startup drive that were created with SuperDuper. Moving around the other icons I have (another partition and my Time Machine backup) do not cause the problem to occur.
Mid-2011 21.5-inch iMac (macOS High Sierra 10.13.6)