Backup fails for clients with MS Exchange or Quickbooks

I have 10 remote systems, backing up to my server over Internet. Other clients are fine, but three remote client, one with MS Exchange and two with Quickbooks, are constantly failing to backup. Please help.

Host Server:
MS Win Server 2008 R2
UrBackup server v 2.2.8
Incremental File Backups Only / Internet

Remote Clients:
Various Windows OS
UrBackup client v 2.2.5

Client 1 Log:
Warnings 03/29/18 01:18 Snapshotting failed because of Writer. Retrying in 30s…
Warnings 03/29/18 01:18 Snapshotting failed because of Writer. Retrying in 30s…
Warnings 03/29/18 01:18 Writer Microsoft Exchange Writer has failure state VSS_WS_FAILED_AT_PREPARE_SNAPSHOT with error VSS_E_WRITERERROR_RETRYABLE. UrBackup will continue with the backup but the associated data may not be consistent.
Warnings 03/29/18 01:18 Writer is in error state during snapshot creation. Writer data may not be consistent. This means the files open by this application (e.g. databases) will be backed up in a crash consistent state instead of a properly shutdown state. Properly written applications can recover from system crashes or power failures.
Errors 03/29/18 04:53 Removing snapshot on “client1” for path “msaccess-data” failed: FAILED
Warnings 03/29/18 04:53 Writer Microsoft Exchange Writer has failure state VSS_WS_FAILED_AT_PREPARE_SNAPSHOT with error VSS_E_WRITERERROR_RETRYABLE
Errors 03/29/18 04:53 Client client1 went offline.
Errors 03/29/18 05:27 Backup failed

Client 2 Log:
Warnings 03/29/18 03:32 Creating hardlink from “S:\UrBackup\client2\180328-0326\Data\quickbooks\client2 Equipment Sales, Inc 1 20 10.QBW.DSN” to “S:\UrBackup\client2\180329-0329\Data\quickbooks\client2 Equipment Sales, Inc 1 20 10.QBW.DSN” failed. Cannot create a file when that file already exists. (code: 183). Loading file…
Warnings 03/29/18 03:32 Creating hardlink from “S:\UrBackup\client2\180328-0326\Data\quickbooks\QBBackupTemp Fri, May 08 2015 08 01 23 AM\client2 Equipment Sales, Inc 1 20 10.QBW.ND” to “S:\UrBackup\client2\180329-0329\Data\quickbooks\QBBackupTemp Fri, May 08 2015 08 01 23 AM\client2 Equipment Sales, Inc 1 20 10.QBW.ND” failed. Cannot create a file when that file already exists. (code: 183). Loading file…
Warnings 03/29/18 03:32 Creating hardlink from “S:\UrBackup\client2\180328-0326\Data\quickbooks\QBBackupTemp Fri, May 08 2015 08 01 23 AM\TempCopyBeforeValidate\client2 Equipment Sales, Inc 1 20 10.QBW.ND” to “S:\UrBackup\client2\180329-0329\Data\quickbooks\QBBackupTemp Fri, May 08 2015 08 01 23 AM\TempCopyBeforeValidate\client2 Equipment Sales, Inc 1 20 10.QBW.ND” failed. Cannot create a file when that file already exists. (code: 183). Loading file…
Warnings 03/29/18 03:34 Error reading current metadata
Errors 03/29/18 03:34 Error saving metadata. Cannot write common metadata.

Client 3 Log:
Warnings 03/29/18 00:20 Error adding sparse file entry. Could not read metadata from S:\UrBackup\client3\180329-0016.hashes\CStone\Images\9605-20071030144934-1-thumbnail.bmp
Warnings 03/29/18 00:20 Error adding sparse file entry. Could not read metadata from S:\UrBackup\client3\180329-0016.hashes\CStone\Images\EMR_PAT-20090618103426-1-original.jp2
Warnings 03/29/18 00:45 Error reading current metadata
Errors 03/29/18 00:45 Error saving metadata. Cannot write common metadata.

There might be more detailed error information in "C:\Program Files\UrBackupServer\urbackup.log". Could you send/attach that?

Also, I am assuming you are backing up the exchange client with components? Have you tried rebooting the client?

Also check why e.g. S:\UrBackup\client3\180329-0016\.hashes\CStone\Images\9605-20071030144934-1-thumbnail.bmp can’t be read…