Network: single computer repeatedly listed in sidebar

I'm having this exact same problem on a mid-2011 21.5" iMac and a mid-2011 11" MacBook Air. This used to happen very occasionally (once every three months maybe) with previous versions of OS X, since updating to Yosemite it's very frequent (several times a day).

Rebooting the computer(s) usually fixes it, sometimes even putting them to sleep and then waking back up, sometimes not.

So I was messing about with my Network settings trying to fix this annoying little bug, and I think I came up with something: try changing the name of the Mac that keeps showing up multiple times in the Finder Sidebar in System Preferences –> Sharing.

When I changed the name of my MacBook Air that had several entries in the Sidebar, this fixed the problem right away. The whole "Shared" part of the Sidebar should disappear for a few seconds, after which it refreshes without the multiple entries.

Whether this is a permanent fix or just a temporary one remains to be seen, but at least it's working for me right now.

On my iMac I was having the same issue. Strangely enough, i went to airport utility and on the base station section I had to log in to my apple id on back to my mac section. this fixed it for me. if you don't have a airport extreme you might turn off back to my mac in iCloud.

That works! I have 2 iCloud accounts - a primary one for purchases and iCloud Drive and secondary for other (due to having a non-Apple account when I started buying things from iTunes long ago - don't ask). I added both to my Airports under "Back to My Mac", and now all is well. Thanks!

I have the same problem, but I don't have Back to my Mac enabled and I don't have any apple IDs configured in Airport Utility.

I'm having the same problem, but the computer name that's showing multiples in my side bar, is the computer that I'm currently using (strange). I'm not using an apple router, so no love from that solution. Wondering if anyone else has found a workaround, until we get an update.

I'm getting the same thing after changing Back to my Mac and Apple IDs in Airport Extreme. Worked for a while, then multiple versions of this very machine in Finder. More tests are necessary, I have 3 Macs.

This might not be an option for everyone, but I turned off File Sharing, renamed the offending computer (the very one on which I was having the problem) to it's original name (sans (#)), and that seems to have stopped the behaviour for now. I'm still hoping that one day I'll be able to use File Sharing again under Yosemite.

I posted this in another thread (mac name with number changing??), but wanted to share my experience with you guys:

I'm having the same problem with my mid-2011 27" iMac on a wireless network with a 2TB Time Capsule router (no ethernet cable connected to any machine). My 2013 MacBook Air on the same wireless network has no problem--its name hasn't changed once. The iMac, on the other hand, consistently changes its name, each time adding a number (2) (3) and so on. If I share the iMac, each of the instances shows up in the MBA's Finder sidebar under shared. Each computer is running Yosemite. Here's what I've tried:

1. Changing the iMac's name under Sharing preferences. For instance, changing the name of the computer from "Name's iMac" to "Office iMac." Didn't work.
2. Resetting the Time Capsule to factory settings. Seems to work only temporarily, but the problem returns.
3. Nuclear option. Reset the Time Capsule to factory settings (again) and performed a clean install of Yosemite on both the iMac and MBA. Thought I had the problem solved with this rather drastic approach, but the problem returned on the iMac today. MBA is still fine. Never turned on sharing after reinstalling Yosemite (thought the problem might have something to do with this), but this doesn't seem to have any effect, either. Problem persists.
4. Per jdslinux's suggestion above, I've enabled BTMM via the AirPort Utility by entering my Apple ID and password (note: I haven't checked BTMM under iCloud settings on either my iMac or MBA), so I'll see if this works. I'm not hopeful, as I had BTMM enabled when the issue first appeared. I'm going to give it a day or two to see if the iMac's name changes again.

I've spoken with Apple Support and they were just as baffled. They recorded all of my settings and network information, sending it the engineers. I'm still awaiting a response (it's been three days--I was told it may take up to four). Really annoying problem. I can't be certain that Yosemite is causing the issue, but I never had this happen in Mavericks with the same network setup.

So, enabling Back to My Mac in the AirPort Utility didn't work. My iMac renamed itself again today, adding the (2) to the computer name. Question: is everyone having this problem using an Apple router?

Having same issue, I blame Yosemite! Help Apple!

Worked for me too! Thanks for the post.