can it be that SOGo connector misses a fallback in case of sync-token is not provided?

Radicale related discussions:
https://github.com/Kozea/Radicale/issues/306

according to debug log of radicale, after SOGo requested a a PROPFIND

<?xml version="1.0"?>
<D:propfind xmlns:D="DAV:" xmlns:x0="http://calendarserver.org/ns/&quot;>&lt;D:prop>&lt;D:resourcetype/>&lt;D:supported-report-set/>&lt;x0:getctag/>&lt;/D:prop>&lt;/D:propfind>

where one

<CS:getctag>"2229d62987e2e5c15c04a6ca52f1b8cd"</CS:getctag

is returned, it asked for REPORT with depth=1

<?xml version="1.0"?><sync-collection xmlns="DAV:"><sync-token/><prop><getetag/><getcontenttype/></prop></sync-collection>

and the result is

<?xml version="1.0"?>
<multistatus xmlns="DAV:">
<response>
<href>/URI/UUID.vcf</href>
<propstat>
<prop>
<getetag>"2229d62987e2e5c15c04a6ca52f1b8cd"</getetag>
<getcontenttype>text/vcard; component=vcard</getcontenttype>
</prop>
<status>HTTP/1.1 200 OK</status>
</propstat>
</response>
</multistatus>

(not containing any sync-token...)

it turned out that Radicale offered in PROPFIND

      <supported-report>
        <report>
          <sync-collection />
        </report>
      </supported-report>

while not really supported internally.

Removed the offering, now it's working.

Issue can be closed now, because it was caused by broken server