Guest user gets error with Office 365 Users connector (SearchUser) in Power Apps

Question

In my Power App I use a combo box where users can choose their own colleagues from a list of employees, filtered by domain name of the email address. This feature works for internal users, but it does not work for guest users in the same tenant. How can this be solved in Power Apps?

This is the code for the items from the combobox:

Sort(
Filter(
    'Office365-gebruikers'.SearchUser({searchTerm: ComboBox1_2.SearchText});
    !IsBlank(Mail) 
    && Lower(Label8_4.Text) in Lower(Mail) 
    && CountA(Split(DisplayName; " ")) > 1
    && !IsMatch(DisplayName; "\d")
    && Not("[PersonalArchive]" in DisplayName)

);
DisplayName;
SortOrder.Ascending)

This works well for the internal users, but not for the guest users.