### **Environment**:

Your OpenProject Version: 11.4.0

Operating System / Browser / OpenProject language:

### **Steps to reproduce:**

Not known. What we do know is that for some Begin of the insertioninstallationsEnd of the insertion Begin of the deletion usersEnd of the deletion some way there exist references Begin of the insertiongroup\_users enries where the user\_id is 0.End of the insertion Begin of the deletion from groups to users (group\_users table) which do no longer exist.End of the deletion

### **Actual Behavior**

No users can be added to or removed from the affected group.

### **Expected Behavior**

One should always be able to add users to (or remove them from) groups.