[Bug] Files nested more than two levels deep don't render correctly

[didoo]

Seems that files that are nested more than two folders deep trigger a strange error in the console:
Error while processing route: show Unexpected token '<', "<!DOCTYPE "... is not valid JSON SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

If you want to reproduce the error see this branch in my fork of the repo:
https://github.com/didoo/field-guide-testing/tree/folder-nesting-bug/docs/03-testing-sub-sub-folder