vdirsyncer incorrectly complains that "Storage was completely emptied"

I successfully synced from local (filesystem on Arch Linux) to remote (radicale server 2.1.8) once. Now on the subsequent runs I get the errer shown below. Note that I am able to sync from the radicale server to a phone. So the remote is not actually empty.

Does it have to do with normalization?

This is vdirsyncer 0.16.3.

debug: Using 1 maximal workers.
Syncing addressbook
debug: PROPFIND http://192.168.1.1:5232/user/addressbook.vcf/
debug: {'User-Agent': 'vdirsyncer/0.16.3', 'Content-Type': 'application/xml; charset=UTF-8', 'Depth': '1'}
debug: <?xml version="1.0" encoding="utf-8" ?>
debug:             <D:propfind xmlns:D="DAV:">
debug:                 <D:prop>
debug:                     <D:resourcetype/>
debug:                     <D:getcontenttype/>
debug:                     <D:getetag/>
debug:                 </D:prop>
debug:             </D:propfind>
debug:             
debug: Sending request...
debug: 207
debug: {'Date': 'Fri, 22 Dec 2017 21:01:02 GMT', 'Server': 'WSGIServer/0.2 CPython/3.6.3', 'DAV': '1, 2, 3, calendar-access, addressbook, extended-mkcol', 'Content-Type': 'text/xml; charset=utf-8', 'Content-Encoding': 'gzip', 'Content-Length': '31299'}
debug: <?xml version='1.0' encoding='utf-8'?>
debug: <multistatus xmlns="DAV:"
xmlns:CR="urn:ietf:params:xml:ns:carddav">
  <response>
    <href>/user/addressbook.vcf/</href>
    <propstat>
      <prop>
        <resourcetype>
          <collection />
        </resourcetype>
      </prop>
      <status>HTTP/1.1 200 OK</status>
    </propstat>
    <propstat>
      <prop>
        <getcontenttype />
        <getetag />
      </prop>
      <status>HTTP/1.1 404 Not Found</status>
    </propstat>
  </response>
  <response>
    <href>
    /user/addressbook.vcf/i1y36nwmmjny43q371o12933nj52x9wg9clw.vcf/</href>
    <propstat>
      <prop>
        <resourcetype>
          <CR:addressbook />
          <collection />
        </resourcetype>
        <getcontenttype>text/vcard</getcontenttype>
        <getetag>"ebf1610a8cd56d4ce5b6aec03d090f23"</getetag>
      </prop>
      <status>HTTP/1.1 200 OK</status>
    </propstat>
  </response>
  <response>
    <href>
    /user/addressbook.vcf/i6g5lzucj5umfdikxgulldltt78wumrwntby.vcf/</href>
    <propstat>
      <prop>
        <resourcetype>
          <CR:addressbook />
          <collection />
        </resourcetype>
        <getcontenttype>text/vcard</getcontenttype>
        <getetag>"9fc7b2fe0990fceb031f6568b04219dd"</getetag>
      </prop>
      <status>HTTP/1.1 200 OK</status>
    </propstat>
  </response>

Many more responses like this before "multistatus" is closed:

</multistatus>

Then loads of messages like this:

debug: Already normalized: '/user/addressbook.vcf/n4vq5kmkwk.vcf/'
debug: Skipping '/user/addressbook.vcf/n4vq5kmkwk.vcf/', is collection.

Finally:

error: addressbook: Storage "addressbook_remote" was completely emptied. If you want to delete ALL entries on BOTH sides, then use `vdirsyncer sync --force-delete addressbook`. Otherwise delete the files for addressbook in your status directory.
error: 1 out of 2 tasks failed.

Start by reproducing the vdirsyncer sync failure with Radicale 2.1.8 and the logged PROPFIND response, then trace response normalization and the storage-empty safety check. Done means a non-empty remote address book is not reported as completely emptied, with regression coverage for this response shape.