WI 4.01 fails to see some URLs, that have working anchor links, properly.
These are reported as 404 or 301 errors.
When the URL looks like href="request-info.html#heading-3", WI reports that the link is broken and lists the link WITHOUT the last letter before the anchor hash.
If this is the link that is checked then the 404 makes sense because it is not the correct link that is checked.
It may check the link with .HTM extension instead of with a .HTML extension.
This can make for a long list of errors. Checking the webpage's HTML code for errors that do not exist is a nuisance!

Best wishes,
Daniel