The background: So I replaced some parts in my PC with slightly newer ones, and I had enough spare parts to make another machine. So I whipped that up with a fresh windows install, and a fresh BOINC install, added it to BAM and that was that.

The problem: Some time later I noticed that one of my PCs wasn't showing up in my hosts lists, and it's always either the new machine, or the machine the parts came from. Syncing either one puts that machine back on the list, and removes the other one.

Troubleshooting so far: I've made sure that the host names are different, that I didn't reuse an old data directory, and I've tried re-attaching to BAM with no success. Next up I'm going to attempt to wipe the data directories of both machines when the work queue is drained. (And hopefully I won't forget to add the results here)

If anyone has any idea what's going on here, please do enlighten me.

Edit: within the acct_mgr_request.xml files I can see that both share the same host_cpid, which is clearly at fault here. Correct me if I'm wrong, but this puts the blame out of the BAM ballpark.

Update: I have re-created the data directories, and one of the hosts now has a different CPID, though syncing either one with BAM still replaces the other one.

Additional details:
BAM Host ID: 605811
Host CPIDs: 7bedb34236a011a27a9562e5711492ce (Vez-SPC) and dfc6dbad55ec1fbb8c0e277d340d89f2 (Vez-PC)
BOINC version: 7.6.33
OS: Microsoft Windows 10 Professional x64

Communication logs: https://www.dropbox.com/s/j8pb44dfqzusrda/BAM%20logs.7z?dl=0

You removed the host authenticator which is an important clue.

Sorry about that, wasn't sure what's sensitive info and what's not. Upon inspection it seems the two do in fact match up (b3f503f38f966c1b86016a67b14ca20a). How would I go about resolving this? Thanks.

Stop one of the hosts, open acct_mgr_login.xml in the BOINC data directory, remove the complete "opaque" section", save, start BOINC, sync with BAM!.

That worked, thanks.