ERROR: This page is using an unprefixed version of template {{Documentation}}

Use {{Wp/syl/Documentation}} instead and replace all occurences of {{Documentation}} in Wp/syl/ prefixed pages by that.
You may like to check 36 templates in Category:Wp/syl/Templates using unprefixed template Documentation first to remove all occurences from those templates which will fix the pages containing those templates too.
Template-info.svg Template documentation

This template is used internally by Template:getalias. It is not intended to be transcluded directly.