Solved by Michela in post #3 
              
              
                Yep, as @Jayant_Parashar said: remove the pruning reparametrization prior to saving the state_dict. 
Yet another solution is to save out the whole model instead of the state dict while it’s still pruned: 
torch.save(pruned_model, 'pruned_model.pth'), and then restore it as pruned_model = torch.load(…