It’s not torch.cat. One of convolutional layers gets input with 67 channels instead of 64.
Given groups=1, weight of size [3, 64, 5, 5]

It means layer you are looking for layer that has following parameters: Conv2d(64, 3, kernel_size=(5,5)) Since you are passing 67 channels, I guess you’re doing cat over 64+3 channels (dim=1) before passing to convolutional layer mentioned above.