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.
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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.