Bonjour chat coming from wrong name but right person

Question

I have multiple users in an organization that use Bonjour to chat with each other. Ever since the update to Yosemite we've been noticing that they aren't able to chat each other directly but in the reverse it works but from the wrong name.
Example:
Mike cannot chat James
Matthew cannot chat Mike
When James chats Mike it comes through as Matthew
This only happens for select users and seems to have no pattern to it. It has even happened mid-chat where the recipient was showing one person then several chat messages later they started coming from someone completely different. We've verified the names are correct in the Contacts app under the "My Card", the computer names are all different, and all are using a verified time server (otherwise multiple other applications would not be working).
I've tried removing ~/Library/Preferences/By Host as well as ~/Library/Preferences/com.apple.ichat* and com.apple.im* and com.apple.messages*

Answer 1

Hi,
There are two possible causes, one of which you mention about the My Card details.
The other is the Computer name in System Preferences > Sharing.
Bonjour Computers automatically show in Shares in the Finder's Side Bar (If you have that preferences set).
They show as the name from the Sharing Pane.
Workplace and campus type settings that update via a central DiskImage can have issues if the computer's names all become the same.
You don't need to remove all those .plists
Concentrate on the com.apple.iChat.Subnet.plist as this keeps the Bonjour info.
Possibly com.apple.imagent.plist as this does the "listening" for incoming invites for all account in Messages and FaceTime.
I would also look at the Contacts App's Preferences and check how many Accounts are active.
I have had issue where iCloud and Yahoo have both been active.  Once I had an issue with On My Mac being active at the same time as iCloud which I have not be able to replicate since I sorted it.
I was Screen Sharing in Messages to Snow Leopard (iChat 5) yesterday concerning another issue about naming.
I used an AIM account not linked to an Address Card on the iMac (Yosemite) to a account on the MacBook Pro/Snow Leopard that is not known to the iMac (it does not appear on any Address Card relating to the MacBook Pro or other contact)
The MacBook Pro/ iChat 5 showed the Buddy as my full name despite it not appearing in any Address card on that computer. (my Names does but not the Apple ID as Valid AIM Screen Name I was using)
Strangely I was using my Main AIM name at one point on the MacBook Pro but the iMac knows that as it is in the Address Card and said I was screen Sharing with the iMac.
Whilst not Bonjour it does show that something has changed about the way Messages in Yosemite looks at the info about who is calling or in some form of connection with you.
At the same time I did notice the Bonjour Buddy Lists displayed the correct info for the "Buddy' on the other computer (Address Book/Contacts app My Card info).
I would check the general Bonjour Sharing first.
8:39 PM      Friday; November 28, 2014
​  iMac 2.5Ghz i5 2011 (Mavericks 10.9)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad