EFCore - Property is not loading at all

Question

Ok, so I tried nearly everything so my last chance is to try to get help here :) As there is a lot smarter and maybe experienced people than myself.

Basically I have structure like this:

Configuration
    SimulationConfiguration
        MachineSimulation (typeof(SimulationSwitch))
            Enabled (ENUM)
        RobotSimulation (typeof(SimulationSwitch))
            Enabled (ENUM)
        ...
        (other parameters of class: Parameter.cs)

I though that it would be quite easy with the EF core. I created DbSets for each object

public DbSet<Configuration> Configurations { get; set; }
public DbSet<SimulationConfiguration> SimulationConfigurations { get; set; }
public DbSet<SimulationSwitch> SimulationSwitches { get; set; }

Also set some initialization in OnModelCreating()

Configuration

modelBuilder.Entity<Configuration>()
            .HasOne(p => (SimulationConfiguration)p.SimulationConfiguration) //Cast due to Interface
            .WithOne()
            .HasForeignKey<SimulationConfiguration>(p => p.IdConfiguration);

SimulationConfiguration

modelBuilder.Entity<SimulationConfiguration>()
            .HasOne<ConfigurationRobotLoader25>()
            .WithOne(p => (SimulationConfiguration)p.SimulationConfiguration)
            .HasForeignKey<SimulationConfiguration>(p => p.IdConfiguration);

SimulationSwitch

modelBuilder.Entity<SimulationSwitch>()
            .Property(p => p.Enable)
            .HasConversion<int>()
            .HasDefaultValue(ESimulationMode.ACTIVE);

I have tried loading it as:

 DatabaseContext.SimulationConfigurations
                .Include(p => p.MachineSimulation)
                .Include(p => p.RobotSimulation)
                .FirstOrDefault(simConf => simConf.IdConfiguration == ConfigurationId);

but it is always empty. but only the SimulationSwitches are empty. Other Parameters load completely fine...

In image above you can see that the green rectangle was loaded fine (also with other properties that I didn't mention) But the red rectangle is some default value. (empty ID, INT value of INACTIVE is 1

I have the same structure with Parameter and it works perfectly fine. But the SimulationSwitches are always empty. (ID = 0)

I am loosing my mind over this. Also tried HasConversion() (and parse it as String) but nothing...

any help will be apreciated