Backups Fail: Error Message "Failed to back up file or folder"

Our backups were running fairly well for awhile, then within the last month, began intermittently failing.  While a couple of successful backups have completed (at least according to the email notification) we receive this type of email failure notice (not always with the same filer/folder name).    

M-W-F task is waiting for user interaction.
Description:
Information: Failed to back up file or folder '\\?\GLOBALROOT\Device\
HarddiskVolumeShadowCopy23\Users\Reji Puthenveetil\Documents\Clients\3D Systems\
AMS PrintSalesFeb17\For Distribution 3DSprint Sales Presentation  0.8.pptx'.
Details:

As you can see, no details were included in the email.  I went into Acronis and changed the number of attempts setting to “silent mode” (saw this on another discussion) and received the email failure notice below this morning.  We also use Acronis on another computer and those backups work fine. Can anyone help me decipher why these backups are failing? Thanks in advance!

1    True Image    4/27/2018 12:01:02 AM    Backup reserve copy attributes: format tib; 
need_reserve_backup_copy false;

2    True Image    4/27/2018 12:01:02 AM    Operation M-W-F started by schedule.

3    True Image    4/27/2018 12:01:03 AM    Backup reserve copy attributes: format tib; 
need_reserve_backup_copy false;

4    True Image    4/27/2018 12:01:03 AM    Operation: Backup

5    True Image    4/27/2018 12:01:03 AM    Priority changed to Low.

6    True Image    4/27/2018 12:01:25 AM    Create Backup Archive From: C:\Users\Reji 
Puthenveetil\Documents\

C:\Users\Reji Puthenveetil\Downloads\

C:\Users\Reji Puthenveetil\Desktop\

C:\Users\Reji Puthenveetil\Pictures\

 To file: "M-W-F_full_b64_s1_v1.tib" Compression:    Normal Exclude:   System files 

7    True Image    4/27/2018 12:01:28 AM    Writing full version to file: M-W-F_full_b64_s1
_v1-2.tib

8    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

9    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

10    True Image    4/27/2018 12:41:55 AM    The network path was not found

11    True Image    4/27/2018 12:41:55 AM    Failed to back up file or folder '\\?\GLOBALROOT\
Device\HarddiskVolumeShadowCopy17\Users\Reji Puthenveetil\Documents\Clients\Lockheed Martin\
Agency Review\Arnold Presentation\We_do_difficult_FINAL.mov'.

Failed to back up the file. (0x170027)

    Path = "\\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy17\Users\Reji Puthenveetil\
Documents\Clients\Lockheed Martin\Agency Review\Arnold Presentation\
We_do_difficult_FINAL.mov",

    $module = "ti_demon_vs_6595"

    Archive::BackupOperationContext::OnError: 

k:\6595\archive\backuper.cpp(805)

Error occurred while reading the file. (0x40001)

    $module = "ti_demon_vs_6595"

    ChunkNTBackupStream: 

k:\6595\file\ntstream_chunker.cpp(273)

Error occurred while writing the file. (0x40003)

    $module = "ti_demon_vs_6595"

    `anonymous-namespace'::ReadStreamData: 

k:\6595\file\ntstream_chunker.cpp(200)

Error occurred while writing the file. (0x40003)

    $module = "ti_demon_vs_6595"

    Archive::WriterImpl::CreateChunk: 

k:\6595\archive\writer.cpp(215)

Error occurred while writing the file. (0x40003)

    Path = "\\GROUPNEWHOUSEPC\BackupDrive\Mon-Fri\M-W-F_full_b64_s1_v1-2.tib",

    $module = "ti_demon_vs_6595"

    TrueImage::Archive::ArchiveMsgWriteCallbackProcessor::ProcessWriteCallback: 

k:\6595\products\imager\archive\impl\operations\archive_message_callback.cpp(1,219)

Error occurred while writing the file. (0x40003)

    function = "WriteFileNoCache",

    $module = "ti_demon_vs_6595"

    win32_nocache_file::Write: 

k:\6595\file\windows\win32_file.cpp(548)

The network path was not found (0xFFF0)

    code = 80070035),

    $module = "ti_demon_vs_6595"

    Common::Error::AddWindowsError: 

k:\6595\common\error.cpp(310): None

12    True Image    4/27/2018 12:41:55 AM    Failed to back up file or folder '\\?\GLOBALROOT\
Device\HarddiskVolumeShadowCopy17\Users\Reji Puthenveetil\Documents\Clients\Lockheed Martin\
Agency Review\Arnold Presentation\We_do_difficult_FINAL.mov'.

: ⎂Retry/⎂Ignore/Ignore ⎂All/⎂Cancel

13    True Image    4/27/2018 12:41:55 AM    The item was skipped.

14    True Image    4/27/2018 12:41:55 AM    The item was skipped.

15    True Image    4/27/2018 12:41:55 AM    The item was skipped.

16    True Image    4/27/2018 12:41:55 AM    The item was skipped.

17    True Image    4/27/2018 12:41:55 AM    The item was skipped.

18    True Image    4/27/2018 12:41:55 AM    The item was skipped.

19    True Image    4/27/2018 12:41:55 AM    The item was skipped.

20    True Image    4/27/2018 12:41:55 AM    The item was skipped.

21    True Image    4/27/2018 12:41:55 AM    Error occurred while backing up.

22    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

23    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

24    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

25    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

26    True Image    4/27/2018 12:41:55 AM    Error occurred while writing the file.

27    True Image    4/27/2018 12:41:55 AM    The network path was not found

28    True Image    4/27/2018 12:41:58 AM    Operation has completed with errors.