Add items from shared public link

I discovered cospend today and tried to add items from a shared public link. Unfortunately this generates the following error message, no matter what I select in the when-area: {"message":"Timestamp (or date) field is required"}

What am I doing wrong? Adding items from a logged-in user or the moneybuster-app work fine. Access rights for the shared link include all three points.

How to reproduce:

• create a project and two members
• share the project via public link
• try to add an item by using the public link