Training network after combining two imds

Hi all,

I'm trying to use a combined dataset to train my network

imds and augImds worked great.

Then I

combine(imds, augImds);

The problem raises when I do

net = trainNetwork(combinedImds, layers, options);

The error pops-up:

Error using trainNetwork: Invalid training data. The output size [1 1 1 2] of the last layer does not match the response size [0 0 1 1].

The thing is that the training works when using imds, or augImds as arguments. But not for combineImds.

Does anyone know how to solve it?

By the way, I haven't found any documentation explaining what are the meaning of these elements in output and response size. My classes are 2, so I wonder the last element for output size represents the # classes. But what are the other elements?

Thanks