title: Internal error when training a model in AUTOML-tables
body: <p>Previously I was able to successfully train a small dataset (approx 45k rows) </p>
  
  <p><code>gs://cloud-ml-tables-data/bank-marketing.csv</code> </p>
  
  <p>using Google AutoML-tables with decent accuracy. Now, I would want to train another dataset with nearly 1 million rows spread across 5 classes. </p>
  
  <p>When I start the training, after sometime I receive "INTERNAL Error".
  I receive the email with the subject </p>
  
  <blockquote>
    <p>AutoML Tables was unable to train model [model_name]</p>
  </blockquote>
  
  <p>and this content:</p>
  
  <blockquote>
    <p>"Hello AutoML Tables Customer, <br> Due to an error, AutoML Tables was
    unable to train <br> model '[model_name]'.<br> Additional Details:
    <br> Resource Name: projects/[...]/locations/us-central1/models/[...]
    <br> Operation State: Failed with errors <br> Error Messages:
    INTERNAL" <br></p>
  </blockquote>
  
  <p>I am not given the details of the error.</p>
  
  <p>What might be causing this? Is this a problem of the dataset that I am using?<br> 
  Any help on how to debug/solve this issue, would be greatly appreciated.<br> Thanks.</p>