Well, there should be a connection between the summed and averaged loss.
If you try to divide the summed loss by the averaged one and the batch size, it looks like your image sizes are approx. 224x224. Would that be a correct guess?
However, back to your original questions. If your model learns fine with a huge loss and doesn’t learn at all with the averaged loss, you could try to increase the learning rate and see, if you can match both training behaviors.