[Help] [BUG?] CloudSync OneDrive files cannot be previewed/opened in TOS File Manager after synchronization

CloudSync is a cloud drive synchronization application for fast and secure data synchronization between your TNAS and cloud drives.
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User avatar
jogas
Posts: 4
Joined: 20 Jun 2026, 16:19
Italy

[Help] [BUG?] CloudSync OneDrive files cannot be previewed/opened in TOS File Manager after synchronization

Post by jogas »

NAS:
TerraMaster F4-425 Plus

OS:
TOS 7 (latest available version)

Application:
CloudSync integrated in TOS 7 (latest version)

Cloud service:
Microsoft OneDrive


Problem description:

I configured CloudSync with the following task:

OneDrive -> NAS

Mode:
"Download only remote files"

Destination folder:

Volume2/main_archive/ONEDRIVE_backup


The synchronization completes successfully.

However, files downloaded by CloudSync cannot be opened correctly from TOS File Manager.


Affected files:
- DOCX
- XLSX
- PDF


Problem:

When I open a file downloaded by CloudSync:

- double-click the file in TOS File Manager;
- a new browser window opens;
- the page remains completely blank.

The file is not displayed in the TOS preview.


The same file works correctly in these cases:

1) Opening from an external PC through SMB:
OK

2) Copying the file using TOS File Manager to another folder on Volume2:
OK

After the copy:
- the preview works;
- the file opens normally.


Tests performed:

1) I created a completely new CloudSync task with:
- new destination folder;
- same OneDrive -> NAS configuration.

The problem happens again.

Therefore the problem is not related to the original folder.

2) Comparison with another OneDrive backup:

I have an older OneDrive backup created by a Synology NAS.

Files from the Synology backup open correctly in TOS File Manager.

Result:

OK:
OneDrive backup created by Synology

Problem:
OneDrive backup created by TerraMaster CloudSync


3) Comparison with FreeFileSync:

Files copied using FreeFileSync from PC to USB disk are correctly readable by TOS File Manager.


Conclusion:

The files are not corrupted.

The problem seems related to the way CloudSync writes files downloaded from OneDrive.

Copying the file internally with TOS File Manager seems to normalize the file and makes it readable again.


Questions:

1. Does CloudSync add any metadata, extended attributes (xattr), ACL or special attributes to downloaded files?

2. Is this a known issue with CloudSync + OneDrive on TOS 7?

3. Is there any configuration option to disable metadata/attribute preservation?


Thank you.
User avatar
EriChan
TM Support
Posts: 310
Joined: 06 Jan 2026, 12:27
China

Re: [Help] [BUG?] CloudSync OneDrive files cannot be previewed/opened in TOS File Manager after synchronization

Post by EriChan »

Thank you for the detailed feedback.

We need to check this issue remotely. Please contact the online technical support staff through the following link to schedule remote technical support:

https://salesiq.zohopublic.com/signatur ... 97d0be8892
To contact our team, please send email to following addresses, remember to replace (at) with @

Technical team: support(at)terra-master.com(for technical support)
Service team: service(at)terra-master.com(for purchasing, return, replacement, RMA service)
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