Maybe we should search official parts before unofficial parts.

[xh38]

When using stud.io's LDraw library, I met a problem when parsing u9421.dat in unofficial parts; it still reference to itself, causing endless recursion.

[Tirus42]

I run into the same problem.
As a workaround: Just delete the u9241.dat in the UnOffical sub directory.

The correct solution should be, that the importer first searches in the UnOffical directory,
but in case of a reference on the same filename, it ignores the already loaded file and loads it from the offical/parent directory.

This seems the intention of the u9241.dat.
This is the rain wheel with the technic axis.

The file in the UnOffical directory adds the rubber friction bands and references the u9241.dat for the wheel itself.