EF Core - How to add an one to zero reference?

Question

I have 4 classes: 1 Machine has many Groups, 1 Group has many Units, 1 Unit has many Components

Now I want the component to have a foreign key of the MachineId to make it easier to search te database later on, but i cant make it work.

public class Machine
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public uint MachineId { get; set; }
    
    public virtual List<Group> Groups { get; set; } = new List<Group?>();
}

public class Component
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public uint ComponentId { get; set; }
    
    public virtual Unit Unit { get; set; }
    public uint? UnitId { get; set; }
    
   
    public virtual Machine Machine { get; set; }
    public uint? MachineId { get; set; }
}   

DatabaseContext:

public class DatabaseContext : DbContext
{
    public DatabaseContext(DbContextOptions options) : base(options)
    {
    }
    public DbSet<Machine> Machines { get; set; }
    public DbSet<Group> Groups { get; set; }
    public DbSet<Unit> Units { get; set; }
    public DbSet<Component> Components { get; set; }


    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Component>()
            .HasOne(m => m.Machine)
            .WithOne()
            .HasForeignKey<Component>(c => c.MachineId)
            .OnDelete(DeleteBehavior.NoAction);
    }
}

DatabaseInitializer:

        Machine machine = new Machine
        {
            Name = "MCTC",
            Connected = true,
            Active = true,
        };
        context.Machines.Add(machine);
        context.SaveChanges();
        
        
        Group group = new Group
        {
            Name = "Group 1",
            Index = 0,
            Present = true,
        };
        machine.Groups.Add(group);
        context.SaveChanges();
        
        Unit unit = new Unit
        {
            Name = "Unit 1",
            Index = 0,
            Present = true,
            UnitType = "MB Balance",
        };
        machine.Groups[0].Units.Add(unit);
        context.SaveChanges();
        
        Component component = new Component
        {
            Name = "Component 1",
            Index = 0,
            Present = true,
            ComponentType = "random"
        };
        machine.Groups[0].Units[0].Components.Add(component);
        context.SaveChanges();

Last "context.SaveChanges()" gives me:

 ---> Microsoft.Data.SqlClient.SqlException (0x80131904): Cannot insert the value NULL into column 'MachineId', table 'MCSmartDb.dbo.Components'; column does not allow nulls. INSERT fails.

Please help...