Ok - looked at the logs (all 8MB of it!) and it looses connection with vCenter (times out) whilst waiting for the snapshot.
As it has lost connection it is not able to delete an old one as it does not know it exists and retries 9 times before giving up and failing (hence the 9 snapshots)
The issue is likely to be with the client experiencing the problem - maybe VMTools is not up to date, maybe it has Apps installed such as SQL or Exchange so its tools.conf need editing to prevent app quiesce
If the others work OK then look into what is wrong with that client - maybe its own VSS components - check its System and Application event logs