Problem: Contacts can only be restored temporarily. There is no way of restoring them afterwards. (heuristic no. 9)
How to reproduce:
Choose a contact in the inbox
The contact is deleted irreversibly.
Restoring the contact is not possible except for the approx. 5 seconds immediately after deletion via the "undo" button on the lower right side of the window.
When deleting contacts, they are moved to the trash. There, you have the possibility to restore them or delete them finally by pressing the "delete" button.