TensorFlow Time Series Tutorial Enhancement Gone Wrong
It seems I was returning multiple features as labels.  I had to modify the dense_1_step function to return a single feature...

def dense_1_step(batch):
  # Shift features and labels one step relative to each other.
  return batch[:-1], batch[-1:,1][0] # take second feature only


To make it the same as the output from the multivariate_data function.