403 Forbidden on "MOVE" when moving files from a groupfolder to a other

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Steps to reproduce

1. Create group folders A & B
2. Both group folders are only set has admin group and no advanced permissions
3. Inside of each folders create a folder ( x inside of A and y inside of B )
4. Share folder x to group G_x and share folder y to group G_y
5. Now set group G_x and G_y to a user
6. Connect to the user and try to cut & paste a file from x folder to y folder

Expected behaviour

The file should be moved to the y folder

Actual behaviour

The file doesn't move from x folder

additional information

The admin can cut & paste without any issue. Seems like it's a permissions issue but the user has the correct permission to do such task.

Server configuration

Operating system:

Debian 12 (Bookworm)

Web server:

nginx 1.22.1

Database:

MariaDB 10.11.4

PHP version:

PHP 8.2.8

Nextcloud version: (see Nextcloud admin page)

27.1.2

Group folders version:

15.3.1

Client configuration

Browser:

Firefox/Chrome

Operating system:

Windows 10/11

Logs

Web server error log

08:31:06||XXXX_XXXX/test.txt -> XXXX_XXXX/test.txt|4|1|1698309029|8a62cf4af9eb252c7f77aa6a70d22186|0|00141238ocvf27t1842r|2|The server replied "403 Forbidden"  on "MOVE"

Nextcloud log (data/nextcloud.log)

{"reqId":"CZhPTU5tBbaFTc45x95s","level":3,"time":"2023-10-26T15:44:35+00:00","remoteAddr":"90.93.71.109","user":"user","app":"core","method":"MOVE","url":"/remote.php/dav/files/user/INTER_AGENCE_COMMUN%20(2)/TEST.txt","message":"unable to rename, source directory is not writable : /srv/nextcloud/nextcloud_DATA/INTER_AGENCE_COMMUN","userAgent":"Mozilla/5.0 (Windows) mirall/3.10.0stable-Win64 (build 20230915) (Nextcloud, windows-10.0.22621 ClientArchitecture: x86_64 OsArchitecture: x86_64)","version":"27.1.2.1","data":{"app":"core"}}

Start with the WebDAV MOVE request described in the reproduction steps and the Nextcloud log message that the source directory is not writable. Trace how group-folder permissions are evaluated for a user with access to both shared subfolders, then verify that the documented non-admin move from x to y succeeds without a 403 while admin behavior remains unchanged.