@spanev , I replaced the nested loop by the loop that you provided. It prints only 3 layers of block3:
0 Conv2d(256, 128, kernel_size=(2, 2), stride=(1, 1))
1 ReLU(inplace)
2 Conv2d(128, 21, kernel_size=(1, 1), stride=(1, 1))

But the architecture of the block is:
self.block3 = nn.Sequential(nn.Conv2d(128, 256, kernel_size=3, stride=1, padding=1),
                                    nn.ReLU(inplace=True),
                                    nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1),
                                    nn.ReLU(inplace=True),
                                    nn.Conv2d(256, 256, kernel_size=3, stride=1, padding=1),
                                    nn.ReLU(inplace=True))

On the good side, if I compare block3_0 and block3_2, the sum of the difference is > 0.