I tried checking if the model parameters contain inf or nan.
So I executed the following code after loading the most recent snapshot
for name,params in generator.named_parameters():
    print("Generator :- isinf : ",name,torch.isinf(params))
    print("Generator :- isNaN : ",name,torch.isnan(params))

for name,params in discriminator.named_parameters():
    print("Discriminator :- isinf : ",name,torch.isinf(params))
    print("Discriminator :- isNaN : ",name,torch.isnan(params))

I ran the main script main.py as follows:
$ python3 main.py | grep True

And this is what I got :
Discriminator :- isNaN :  conv_img.bias tensor([True, True, True, True, True, True, True, True, True, True, True, True,
        True, True, True, True, True, True, True, True, True, True, True, True,
        True, True, True, True, True, True, True, True], device='cuda:0')
Discriminator :- isNaN :  block0.gamma tensor([True], device='cuda:0')
Discriminator :- isNaN :  block0.conv_r.0.weight tensor([[[[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]],
         [[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]],
         [[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]],
         [[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]],
         [[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]],
         [[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]]],
        [[[True, True, True, True],
          [True, True, True, True],
          [True, True, True, True],
          [True, True, True, True]],
        .....
        .....

It looks like all the parameters in the discriminator model have become nan.