AH01630: client denied by server configuration

Hi,

Apache generate lots of warnings like below on some files within the httpdocs:

[authz_core:error] AH01630: client denied by server configuration: /var/www/vhosts/domain.com/httpdocs/
wp-content/themes/***/css/custom_style.php

Any idea how to fix this? I found this in
/usr/local/psa/admin/conf/templates/default/server.php:

<Directory "<?php echo $VAR->server->webserver->vhostsDir ?>">
AllowOverride "<?php echo $VAR->server->webserver->apache->allowOverrideDefault ?>"
Options...

AH01630: client denied by server configuration