No permissions for just one folder in external storage

I have a strange problem when accessing home directory via an external storage connected to a CIFS share on my file server. I have the ‘You don’t have permissions to upload or create files here’ message, but only on the ‘Documents’ folder while this directory has the same ACLs as others directories.
The problem appear on fresh installations of Nextcloud (V 21.0.0 and V 20.0.6) and with the files_external versions 1.11.1 and 1.12.
But, that’s what is weird, the problem doesn’t appear in a older version of nextcloud (V 18.0.1) and files_external version 1.9.0.
It seems to be a bug.

Le « home » directory distant est protégé par prudence au montage direct. J’ai utilisé un sous directory comme racine.