Solved by KFrank in post #2 
              
              
                Hello Ahmed! 

Yes, this is, in effect, what will happen. 
Summing the losses is the approach I would take.  I would probably 
include relative weights: loss = w1 * loss1 + w2 * loss2. 
Note, that loss1 does not depend on the weights in modules D and 
E, so backpropagating loss1 + loss2 will have th…