Calendar App, one calendar makes an error

Hi,

i´ve updated the calendar app to Version 1.5.1. Nextcloud is 11.0.0.
There are two calenders created. One of them is shown and everything looks fine. But the other one is loading and loading and loading.
When i look in the log of nextcloud i see following error which i don´t understand. Someone who can help me?

[code] Sabre\VObject\InvalidDataException: Unsupported VALUE parameter for DTEND property. You supplied “”

/www/htdocs/.../cloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php - line 453: Sabre\VObject\Document->createProperty('DTEND', NULL, Array)
/www/htdocs/.../cloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php - line 234: Sabre\VObject\Parser\MimeDir->readProperty('DTEND;TZID=Euro...')
/www/htdocs/.../cloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php - line 217: Sabre\VObject\Parser\MimeDir->parseLine('DTEND;TZID=Euro...')
/www/htdocs/.../cloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php - line 181: Sabre\VObject\Parser\MimeDir->parseLine('BEGIN VEVENT')
/www/htdocs/.../cloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php - line 89: Sabre\VObject\Parser\MimeDir->parseDocument()
/www/htdocs/.../cloud/3rdparty/sabre/vobject/lib/Reader.php - line 46: Sabre\VObject\Parser\MimeDir->parse('BEGIN VCALENDAR...', 0)
/www/htdocs/.../cloud/3rdparty/sabre/dav/lib/CalDAV/Backend/AbstractBackend.php - line 142: Sabre\VObject\Reader read('BEGIN VCALENDAR...')
/www/htdocs/.../cloud/apps/dav/lib/CalDAV/CalDavBackend.php - line 1123: Sabre\CalDAV\Backend\AbstractBackend->validateFilterForObject(Array, Array)
/www/htdocs/.../cloud/apps/dav/lib/CalDAV/Calendar.php - line 248: OCA\DAV\CalDAV\CalDavBackend->calendarQuery('2', Array)
/www/htdocs/.../cloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php - line 624: OCA\DAV\CalDAV\Calendar->calendarQuery(Array)
/www/htdocs/.../cloud/3rdparty/sabre/dav/lib/CalDAV/Plugin.php - line 250: Sabre\CalDAV\Plugin->calendarQueryReport(Object(Sabre\CalDAV\Xml\Request\CalendarQueryReport))
[internal function] Sabre\CalDAV\Plugin->report('{urn ietf param...', Object(Sabre\CalDAV\Xml\Request\CalendarQueryReport), 'calendars/Benny...')
/www/htdocs/.../cloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105: call_user_func_array(Array, Array)
/www/htdocs/.../cloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php - line 718: Sabre\Event\EventEmitter->emit('report', Array)
[internal function] Sabre\DAV\CorePlugin->httpReport(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/www/htdocs/.../cloud/3rdparty/sabre/event/lib/EventEmitterTrait.php - line 105: call_user_func_array(Array, Array)
/www/htdocs/.../cloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 479: Sabre\Event\EventEmitter->emit('method REPORT', Array)
/www/htdocs/.../cloud/3rdparty/sabre/dav/lib/DAV/Server.php - line 254: Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
/www/htdocs/.../cloud/apps/dav/lib/Server.php - line 227: Sabre\DAV\Server->exec()
/www/htdocs/.../cloud/apps/dav/appinfo/v2/remote.php - line 30: OCA\DAV\Server->exec()
/www/htdocs/.../cloud/remote.php - line 165: require_once('/www/htdocs/w00...') 

[/code]

I think there is a bad date in the calender, but how can i fix it?

Greetings
MC

Edit: Also after downgrade to 1.5. and 1.4.1.

Can you retry with the current NC version (11.0.2) and the calendar app? If you still see this error, please report it to the bugtracker on https://github.com/nextcloud/server/issues.