I am becoming bald from tearing my hair on this issue...

What we have :

SharePoint 2016 Farm with :

  • WFE Server "web1"
  • Application server "app1"
  • SQL Server "sql"
  • Site collections with subsites.
  • Classic experience for all libraries. We tried to keep the url short thoughout each site collection (like sites/w/L1)

What is the issue :

When trying to upload a file via Web (in library, click on "+ Upload a document", browse and ok), it works, for file from 0 to 250 Mo. No big deal.

When trying to upload a file via File Explorer (in library, Library tab on ribbon, click on "Open in File explorer", and drag and drop from Desktop), the upload randomly fails. (I know uploading through File Explorer is not the advised way, but my users have to upload files by bulk. And sometimes, big files.)

It gives us this error :

Error message when trying to upload a file using File Explorer

Rough translation from french :

An unexpected error prevent you to copy this file. If the issue lasts, use the error code to search help on this error. Error 0x80070780 : system can't access to the file.

But the behavior is really strange and we do not reproduce it 100% of the times we try. It is randomly occuring for all users, for every site collection we tested it on. We get this error for lots of different files, from simple .txt file of 8octets to Word files of 100Mo.

We have tried a lot and can not reproduce the exact steps everytime.

What I tried

Tying to reproduce it to find the cause, but could not reproduce it faithfully. I tried to restart the WebClient service on my side, but it did nothing.

So, do you have any idea on how to solve the 0x80070780 error and allow my users to upload files from File Explorer?

Please help me with your science !

2 Answers 2


I am not a fan of File Explorer to upload documents/folders. I have seen several times that the upload requests completes without errors but files are actually missing or have 0 kB size. In your case you do have an error message. That is the good news, the bad news is that you need to figure out what is going on.


  1. Can you install a tool like Fiddler to check the web traffic? https://www.telerik.com/fiddler
  2. Do the IIS logs on the front-end server provide information what is going on?
  3. Can you temporarily disable the anti-virus scanner on the client computer?
  4. Is the traffic between the client and the SharePoint server routed via a proxy or do you have a direct connection? If there is a proxy in between you may want to change the client configuration to take that component out of the equation.

As you may not know there are browser-based apps that can replace File Explorer, e.g. here You can upload folder structures, multiple documents, set metadata, ...


  • Thanks for your time on this,Paul, really appreciate it. I'll install Fiddler and check the IIS logs. I have to add that everything worked fine for more than a year before now going nuts.So, I am not sure the anti-virus is involved (or might it be an update causing it?) I am asking about the proxy. Thanks.
    – Gaelle
    Aug 7, 2020 at 12:43

There're some reasons may cause this issue.

1.Corrupted or damaged System files.

2.Hard disk errors or bad sectors.

3.The file or directory is corrupted and unreadable.

4.Virus or malware infection.

Here's a reference for you to troubleshooting the issue.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.