When you have a circular pipeline, you want to make sure that you disconnect the result. In general, if you don’t disconnect it, you will run into problems. In your case, you want to call Add->Filter->DisconnectPipeline(); [1][2] after calling Update().
[1] How to _really_ disconnect pipeline?
[2] https://itk.org/pipermail/insight-users/2002-October/001368.html