I forgot to mention that 755 should not be used for .ssh but to use 700, the script v-add-user-sftp-key must be modified to set a new acl:
sed -i.ori -e '/^AUTHKEY_FILE=.*authorized_keys/a SSH_DIR="$HOMEDIR/$user/.ssh"' -e '/^chown "hestiaweb": "${PRVKEY_FILE}"/a \\nsetfacl -m u:hestiaweb:--x "${SSH_DIR}" > /dev/null 2>&1' /usr/local/hestia/bin/v-add-user-sftp-key
If you already modified /usr/local/hestia/web/fm/configuration.php you must also edit it and remove the modification.
If you didn’t modify it yet, you can execute this command:
sed -i.ori '/\/\/ filemanager also requires .ssh chmod o+x/{N;N;d}' /usr/local/hestia/web/fm/configuration.php
So you can change .ssh perms to 700.
chmod 700 /home/*/.ssh