Unable to create and add files and folders

Hello,

I'm experiencing a persistent problem on our Nextcloud server, where our Guest users are unable to upload files or create folders, consistently receiving an HTTP 403 (Access Denied) error. This problem directly affects sharing functionality and collaboration with external users. Below you'll find a detailed description of the problem, the error messages observed, and the checks and resolution attempts already undertaken.

Problem description :
Guest users, when attempting to upload a file or create a folder via the web interface receive an HTTP 403 error. This problem seems to be specific to Guest users, as regular users do not encounter similar issues.

Error messages observed :
Attempted actions by Guest users generate the following error messages in Nextcloud access logs:

When attempting to upload a file: "PUT /remote.php/dav/files/myaccount%40gmail.com/Capture%20d%E2%80%99e%CC%81cran%202022-09%20a%CC%80%2014.31.48.png HTTP/1.1" 403 1403
When attempting to create a folder: "MKCOL /remote.php/dav/files/myaccount%40gmail.com/New%20folder HTTP/1.1" 403 1403

Actions already taken :
File system permissions have been checked and adjusted to ensure that the web server user has the appropriate rights to write to the Nextcloud data directory.

No specific rules blocking PUT or MKCOL methods were identified in the web server configuration files or in Nextcloud's .htaccess file.

No applications or configurations within Nextcloud were identified as being able to restrict the actions of Guest users. The list of installed applications was provided to examine possible sources of conflict.

File upload and folder creation functions work normally for regular users, indicating that the problem is specific to Guest users.

I'm asking for your help in identifying and resolving the problem of access denied to Guest users. Any guidance or suggestions on further steps to be taken would be greatly appreciated. Also, if any additional information or logs are needed, please let me know.

Thank you in advance for your time and assistance.

Start by reproducing the guest-user PUT and MKCOL requests described in the issue, then compare their access-log entries with those from a regular user. Review the guest sharing and permission configuration using the listed checks as context; done means identifying the cause of the 403 responses and documenting a verified resolution.