Models referenced by file path - Who is Willy?

[Alexander U.]

I have installed the optional LEGO Model LDraw files.

This is how the Fort Legoredo looks like: https://i.imgur.com/m9RkjRE.png

Certain Technic models (e.g. 42039) look even worse.

The issue seems to be caused by model references that do not resolve to a file; one of the paths is shown in the tooltip.

So: Who is Willy?