Currently DAV errors have incorrect namespace of error tag "DAV" but it should "DAV:" with a colon.
Example of error I get:
HTTP/1.1 403 Forbidden

content-length: 93
content-type: application/xml; charset="utf-8"

<?xml version="1.0" encoding="utf-8"?>
<D:error xmlns:D="DAV">sequences don't match</D:error>
RFC https://datatracker.ietf.org/doc/html/rfc4918#section-14 in section 14 says that "All elements defined here are in the "DAV:" namespace."
Section 14.5 describes the error element.
All examples of using error element are desribed as

<D:error xmlns:D="DAV:">
...
</D:error>