Solved by jpeg729 in post #4 
              
              
                Again, I am guessing… 
One of these outputs has passed through one Conv1d, the other has passed through two Conv1d’s. 
I think the problem is that each Conv1d hasn’t got enough padding, so the input sequence got shortened to 60 timesteps after one Conv1d, and then to 56 timesteps after the two Conv1…