Hello Philip,
thank you for reporting this and your analysis!

Is this on CPU or GPU?
What is the dimension of the tensor you do the log_softmax on?
Ideally, we’d get some specific inputs demonstrating a regression. Maybe the following works:
If you take a somewhat pre-trained model and run it on 0.4.1 and 1.0.0, do can you spot any differences between the log_softmax output, the loss, or the gradients of the logits (use logits.retain_grad() between forward and backward to keep them around)?

Best regards
Thomas