Something wrong with the volume's CNID DB using temporary DB

after upgrading Pro BE from 4.2.11 to 4.2.13 I got the same error message when opening time machine.
(at that moment I already had another share from the Pro BE mounted, don't know whether that matters)

I then looked and found this topic, and downgraded to 4.2.11.

I downloaded the Pro BE logs (after the error, and once again after downgrading and opening time machine again),
and saw in afp.log the following error lines that seem related:

afp.log:9978:Aug 18 22:24:45.627137 afpd[3480] {cnid_dbd.c:325} (E:CNID): dbd_rpc: Error reading header from fd (db_dir /c/.timemachine): Resource temporarily unavailable
afp.log:9979:Aug 18 22:24:56.626994 afpd[3480] {cnid_dbd.c:325} (E:CNID): dbd_rpc: Error reading header from fd (db_dir /c/.timemachine): Resource temporarily unavailable
afp.log:9980:Aug 18 22:24:56.627110 afpd[3480] {cnid_dbd.c:411} (E:CNID): transmit: Request to dbd daemon (db_dir /c/.timemachine) timed out.
afp.log:9981:Aug 18 22:24:56.627148 afpd[3480] {file.c:246} (E:AFPDaemon): Reopen volume /c/.timemachine using in memory temporary CNID DB.

also the system.log on the mac seems to contain related error messages.

Aug 18 22:24:34 Hostname kernel[0]: AFP_VFS afpfs_mount: /Volumes/ReadyNAS, pid 826
Aug 18 22:24:34 Hostname [0x0-0xc00c].com.apple.finder[167]: Unexpected reply from backup server - ignored
Aug 18 22:24:34 Hostname /System/Library/CoreServices/backupd[825]: Mounted network destination using URL: afp://ReadyNAS@nas-EA-29-C1.local/ReadyNAS
Aug 18 22:24:34 Hostname /System/Library/CoreServices/backupd[825]: Backup destination mounted at path: /Volumes/ReadyNAS
Aug 18 22:25:05 Hostname hdiejectd[836]: running
Aug 18 22:25:05 Hostname [0x0-0xc00c].com.apple.finder[167]: Unexpected reply from backup server - ignored
Aug 18 22:25:06 Hostname /System/Library/CoreServices/backupd[825]: Disk image /Volumes/ReadyNAS/Hostname_01234567890abcdef.sparsebundle mounted at: /Volumes/Backup of Hostname
Aug 18 22:26:33 Hostname [0x0-0x58058].com.apple.systempreferences[850]: Unexpected reply from backup server - ignored
Aug 18 22:26:36 Hostname [0x0-0xc00c].com.apple.finder[167]: Unexpected reply from backup server - ignoredUnexpected reply from backup server - ignored
Aug 18 22:26:36 Hostname [0x0-0xb00b].com.apple.systemuiserver[166]: Unexpected reply from backup server - ignored
Aug 18 22:26:36 Hostname [0x0-0x58058].com.apple.systempreferences[850]: Unexpected reply from backup server - ignored

I think I have seen the 'Unexpected reply from backup server - ignored' before, but typically at most one at a time.

Axel.