EF Core 2 prova a creare lo stesso tavolo due volte

Ho un progetto con EF Core 2. Ho creato una migrazione. Durante l'esecuzione della migrazione viene restituito con il seguente errore:

infoinfo:    System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'Clients' in the database.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite, String methodName)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.Execute(IRelationalConnection connection, DbCommandMethod executeMethod, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
ClientConnectionId:718d9d47-c2e4-4bf5-9e15-165884a5ff11
Error Number:2714,State:6,Class:16
infoerror:   There is already an object named 'Clients' in the database.
: Microsoft.EntityFrameworkCore.Database.Command[200101]
  Executed DbCommand (8ms) [Parameters=[@p0='?' (Size = 400), @p1='?' (Size = 400), @p2='?' (Size = 4000), @p3='?', @p4='?', @p5='?' (Size = 400), @p6='?' (Size = 400), @p7='?' (Size = 4000), @p8='?', @p9='?', @p10='?' (Size = 400), @p11='?' (Size = 400), @p12='?' (Size = 4000), @p13='?', @p14='?', @p15='?' (Size = 400), @p16='?' (Size = 400), @p17='?' (Size = 4000), @p18='?', @p19='?'], CommandType='Text', CommandTimeout='30']
  SET NOCOUNT ON;
  DECLARE @inserted0 TABLE ([Id] int, [_Position] [int]);
  MERGE [Options] USING (
  VALUES (@p0, @p1, @p2, @p3, @p4, 0),
  (@p5, @p6, @p7, @p8, @p9, 1),
  (@p10, @p11, @p12, @p13, @p14, 2),
  (@p15, @p16, @p17, @p18, @p

Questo è il mio DbContext:

namespace MyProject.Data
{
    public class MyProjectContext : DbContext
    {
        public MyProjectContext(DbContextOptions<MyProjectContext> options)
            : base(options)
        {
        }

        public DbSet<ExtensionBasicQuotation> ExtensionBasicQuotations { get; set; }
        public DbSet<ExtensionSpecifiedQuotation> ExtensionSpecifiedQuotations { get; set; }
        public DbSet<Client> Clients { get; set; }
        public DbSet<Option> Options { get; set; }
        public DbSet<SpecifiedQuotationAttachment> SpecifiedQuotationAttachments { get; set; }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder);

            builder.ApplyConfiguration(new ClientConfiguration());
            builder.ApplyConfiguration(new ExtensionBasicQuotationConfiguration());
            builder.ApplyConfiguration(new ExtensionSpecifiedQuotationConfiguration());
            builder.ApplyConfiguration(new OptionConfiguration());
        }
    }
}

Esiste una sola migrazione e la migrazione ha una sola funzione CreateTable per la tabella Clients .

migrationBuilder.CreateTable(
                name: "Clients",
                columns: table => new
                {
                    Id = table.Column<int>(type: "int", nullable: false)
                        .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
                    Address = table.Column<string>(type: "nvarchar(500)", maxLength: 500, nullable: true),
                    City = table.Column<string>(type: "nvarchar(200)", maxLength: 200, nullable: true),
                    Email = table.Column<string>(type: "nvarchar(200)", maxLength: 200, nullable: true),
                    Name = table.Column<string>(type: "nvarchar(200)", maxLength: 200, nullable: true),
                    Phone = table.Column<string>(type: "nvarchar(20)", maxLength: 20, nullable: true),
                    Postcode = table.Column<string>(type: "nvarchar(20)", maxLength: 20, nullable: true)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Clients", x => x.Id);
                });

Perché la tabella Client viene creata due volte?