[Bug]: After mounting SFTP in Nextcloud, copying a folder often results in some files missing when viewed, even though the folder size appears correct. Running files:scan --all is required to make all files appear properly.

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

After mounting SFTP in Nextcloud, copying a folder often results in some files missing when viewed, even though the folder size appears correct. Running files:scan --all is required to make all files appear properly.

At the same time, the images inside do not trigger automatic preview generation by Preview Generator.

Steps to reproduce

1. Mount SFTP,
2. Copy a folder containing multiple subfolders and a large number of images to a directory in Nextcloud,
3. After completion, some folders or files are always missing when viewing the directory. Running files:scan --all is required, and no preview images are generated.

Expected behavior

Display all folders and files, and automatically generate preview images.

Nextcloud Server version

31

Operating system

Debian/Ubuntu

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start by reproducing the SFTP mount and folder-copy workflow with nested folders and many images, then compare the directory contents before and after running files:scan --all. Investigate the copy path and Preview Generator behavior; done means all copied files and folders are visible without a scan and previews are generated automatically.