Entity Framework 6.1 Error: Schema specified is not valid.

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entity-framework

I have a database that has a many to many between 2 tables. This works fine. I now need to add a second many to many between the same tables. So, following the same approach as with the first relationship, compiling is not problem but adding a migration to support the schema change gives me an error.

First relationship definition:

modelBuilder.Entity<Hazard>()
    .HasMany(r => r.RiskEliminationRecommendations)
    .WithMany(h => h.Hazards)
    .Map(
    h =>
    {
        h.MapLeftKey("Hazard_id");
        h.MapRightKey("Option_id");
        h.ToTable("HazardEliminationOptions");
    });

uses the Hazard and RiskEliminationOption models (I removed the rest of the class for brevity's sake!):

(Hazard class)

public virtual ICollection<RiskEliminationOption> RiskEliminationRecommendations { get; set; }

(RiskEliminationOption class)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace RAdb.Models
{
    public class RiskEliminationOption
    {
        public int Id { get; set; }
        public string ResourceId { get; set; }
        public string Description { get; set; }
        public bool Active { get; set; }
        public virtual ICollection<Hazard> Hazards { get; set; }
    }
}

If I now add a further many-to-many definition in the OnModelCreating function of my DB Context class as follows:

modelBuilder.Entity<Hazard>()
    .HasMany(o => o.NewEliminateRiskRecommendations)
    .WithMany(h => h.Hazards)
    .Map(
    h =>
    {
        h.MapLeftKey("Hazard_id");
        h.MapRightKey("Option_id");
        h.ToTable("HazardNewRiskEliminationOptions");
    });

The application will build perfectly but when I come to scaffold the migration I get the following error:

PM> Add-Migration ReAssessment1
System.Data.Entity.Core.MetadataException: Schema specified is not valid. Errors: The relationship 'RAdb.Models.Hazard_RiskEliminationRecommendations' was not loaded because the type 'RAdb.Models.RiskEliminationOption' is not available.
   at System.Data.Entity.Core.Metadata.Edm.CodeFirstOSpaceTypeFactory.LogError(String errorMessage, EdmType relatedType)
   at System.Data.Entity.Core.Metadata.Edm.OSpaceTypeFactory.CreateAndAddNavigationProperty(StructuralType cspaceType, StructuralType ospaceType, NavigationProperty cspaceProperty)
   at System.Data.Entity.Core.Metadata.Edm.OSpaceTypeFactory.<>c__DisplayClass18.<TryFindNavigationProperties>b__14()
   at System.Data.Entity.Core.Metadata.Edm.CodeFirstOSpaceLoader.LoadTypes(EdmItemCollection edmItemCollection, ObjectItemCollection objectItemCollection)
   at System.Data.Entity.ModelConfiguration.Edm.DbDatabaseMappingExtensions.ToMetadataWorkspace(DbDatabaseMapping databaseMapping)
   at System.Data.Entity.Internal.CodeFirstCachedMetadataWorkspace..ctor(DbDatabaseMapping databaseMapping)
   at System.Data.Entity.Infrastructure.DbCompiledModel..ctor(DbModel model)
   at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext)
   at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input)
   at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
   at System.Data.Entity.Internal.LazyInternalContext.get_ModelBeingInitialized()
   at System.Data.Entity.Infrastructure.EdmxWriter.WriteEdmx(DbContext context, XmlWriter writer)
   at System.Data.Entity.Utilities.DbContextExtensions.<>c__DisplayClass1.<GetModel>b__0(XmlWriter w)
   at System.Data.Entity.Utilities.DbContextExtensions.GetModel(Action`1 writeXml)
   at System.Data.Entity.Utilities.DbContextExtensions.GetModel(DbContext context)
   at System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration, DbContext usersContext)
   at System.Data.Entity.Migrations.DbMigrator..ctor(DbMigrationsConfiguration configuration)
   at System.Data.Entity.Migrations.Design.MigrationScaffolder..ctor(DbMigrationsConfiguration migrationsConfiguration)
   at System.Data.Entity.Migrations.Design.ToolingFacade.ScaffoldRunner.Run()
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Scaffold(String migrationName, String language, String rootNamespace, Boolean ignoreChanges)
   at System.Data.Entity.Migrations.AddMigrationCommand.Execute(String name, Boolean force, Boolean ignoreChanges)
   at System.Data.Entity.Migrations.AddMigrationCommand.<>c__DisplayClass2.<.ctor>b__0()
   at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
Schema specified is not valid. Errors: The relationship 'RAdb.Models.Hazard_RiskEliminationRecommendations' was not loaded because the type 'RAdb.Models.RiskEliminationOption' is not available.
PM> 

Can anyone explain to me what I am doing wrong here?

Many thanks in advance,
Chris.