Delegated for former employee

Summary:

Delegated for former employee could not find the former employee in Expense

We have had some issues, where delegated has been setup for former employees. But the delegated could not find them in Expense.
But it is not all former employees, where the delegated couldn't find them.

How we can solve these issues and why does the problem occur only on some former employees?

I have attached a document, where you can see who I'm delegated for and who I'm able to see in the dropdown menu in Expense.

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