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

Use {{Wy/ml/Documentation/docname}} instead and replace all occurences of {{Documentation/docname}} in Wy/ml/ prefixed pages by that.
You may like to check 19 templates in Category:Wy/ml/Templates using unprefixed template Documentation/docname first to remove all occurences from those templates which will fix the pages containing those templates too.
Template:Wy/ml/Banner/doc|action=edit&preload=Template:Documentation/preload}} create]]
Template documentation