Inclua vários irmãos no nível
_dbSet
.Include(tiers => tiers.Contacts).ThenInclude(contact => contact.Titre)
.Include(tiers => tiers.Contacts).ThenInclude(contact => contact.TypeContact)
.Include(tiers => tiers.Contacts).ThenInclude(contact => contact.Langue);
// etc.
Anxious Albatross