MongoDB.Driver.MongoCommandException: Command update failed: BSON field 'OperationSessionInfo.txnNumber' is a duplicate field.
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.ProcessResponse(ConnectionId connectionId, CommandMessage responseMessage)
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.ExecuteAsync(IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.Server.ServerChannel.ExecuteProtocolAsync[TResult](IWireProtocol`1 protocol, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.RetryableWriteOperationExecutor.ExecuteAsync[TResult](IRetryableWriteOperation`1 operation, RetryableWriteContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.BulkUnmixedWriteOperationBase`1.ExecuteBatchAsync(RetryableWriteContext context, Batch batch, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.BulkUnmixedWriteOperationBase`1.ExecuteBatchesAsync(RetryableWriteContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.BulkMixedWriteOperation.ExecuteBatchAsync(RetryableWriteContext context, Batch batch, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.BulkMixedWriteOperation.ExecuteAsync(IWriteBinding binding, CancellationToken cancellationToken)
   at MongoDB.Driver.OperationExecutor.ExecuteWriteOperationAsync[TResult](IWriteBinding binding, IWriteOperation`1 operation, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.ExecuteWriteOperationAsync[TResult](IClientSessionHandle session, IWriteOperation`1 operation, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.BulkWriteAsync(IClientSessionHandle session, IEnumerable`1 requests, BulkWriteOptions options, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionBase`1.UpdateOneAsync(FilterDefinition`1 filter, UpdateDefinition`1 update, UpdateOptions options, Func`3 bulkWriteAsync)

var client = new MongoClient(ConnectionString);
 
var database = client.GetDatabase(DatabaseName);
 
var Coupons = database.GetCollection<Coupon>("Coupons");
 
var Books = database.GetCollection<Book>("Books");
 
var session = await database.Client.StartSessionAsync();
session.StartTransaction();
 
try {
     Coupons.UpdateOneAsync(session, couponsFilter, couponsUpdate);//Exception happens at this line

     Books.UpdateOneAsync(session, booksFilter, booksUpdate); 

     await session.CommitTransactionAsync();
} catch (Exception ex) {
     await session.AbortTransactionAsync();
 
     Console.WriteLine(ex.StackTrace);
}