Hello Saguaros,
After some investigations i can tell you, these errors only appear with joomla reporting on maximum level. So it may not have priority, but please keep this in mind. You can see these errors now on my testsite in menu "Veranstaltungen" from this post.
But for second, if i go to the events, it does not show me the "show past events" or sorting options, that were used to show before. Please can you have look at this?
Thank you and best regards