In libvcalendar.php line 1345:

foreach ($transitions as $i => $trans) { ... if ($i == 0) { $tzfrom = $trans['offset'] / 3600; continue; }

If transitions is size 1 , No STANDARD component is created, but is needed according to RFC 2445 , see http://www.kanzaki.com/docs/ical/vtimezone.html
Without STANDARD component I would get BAD REQUEST in Radicale and cannot put in event.