Whiteboard Card Selector has still deleted items

I have a “Insights” Database, filled with some 30 entries. A port of those I deleted again.
When I add a card to a whiteboard in the same space and select the Insights database, the deleted items are still shown and can be selected. The card show then that the item is not found.
In the selection list are not the same ids as in the original database, so I assume it is an unrefreshed cache somewhere?
After renaming the original database, no items are shown in the list.