I have run this twice and it has given me a NaN. The first time I thought it was an overclock issue, but I turned that off and it happened again. Is this a bug?
Here is the model, the first RNN is a simple RNN and the second is a GRU.
Both RNNs are using ReLU and the first has had the code altered to set return_sequences=True.
Is there anything else that you need?