I haven’t been able to make a pure pytorch script reproducing the error since it would be non-trivial because the code involved with the error extends a pytorch-lightning class (which extends nn.Module), but someone in another forum has suggested that the problem is that Pytorch does not support self.to('cuda') in multi-GPU scenarios, and you have to specify with 'cuda:n' where n is the device index. Do you know if this is true?