Solved by ptrblck in post #2 
              
              
                nn.CrossEntropyLoss expects raw logits, so you should remove the self.softmax from the forward method. 
Assuming your current model output represents: [batch_size=88, seq_len=498, nb_classes=3], you would have to permute the output so that it has the shape [batch_size, nb_classes, seq_len] via outpu…