RuntimeError about loss.backward()

 File "/data/ch/CAMUS/skip_clstm/train_motion_warp.py", line 116, in train_net
    loss.backward()
  File "/data/ch/anaconda3/envs/tensorflow/lib/python3.6/site-packages/torch/tensor.py", line 107, in backward
    torch.autograd.backward(self, gradient, retain_graph, create_graph)
  File "/data/ch/anaconda3/envs/tensorflow/lib/python3.6/site-packages/torch/autograd/__init__.py", line 93, in backward
    allow_unreachable=True)  # allow_unreachable flag
  File "/data/ch/anaconda3/envs/tensorflow/lib/python3.6/site-packages/torch/autograd/function.py", line 77, in apply
    return self._forward_cls.backward(self, *args)
  File "/data/ch/anaconda3/envs/tensorflow/lib/python3.6/site-packages/torch/utils/checkpoint.py", line 99, in backward
    torch.autograd.backward(outputs, args)
  File "/data/ch/anaconda3/envs/tensorflow/lib/python3.6/site-packages/torch/autograd/__init__.py", line 93, in backward
    allow_unreachable=True)  # allow_unreachable flag
RuntimeError: vector::_M_range_check: __n (which is 1923827846) >= this->size() (which is 5)

Anyone can help me ? Thanks in acvance !