Solved by ffuuugor in post #2 
              
              
                Hi! 
Yeah, that’s somewhat expected - we never migrated to register_full_backward_hook  since it was released in PyTorch 1.8. 
We’ll fix that soon (thanks for raising this!). But in the meantime, as  far as I’m aware, this shouldn’t create any problems (at least with 1.9) - all our tests are passing…