@krrishabh
I think version mismatch might be the root cause.
If you saved your .pt with 1.3.1, please use the same version of libtorch to load it.
We have a similar issue here,
‘https://github.com/pytorch/pytorch/issues/39623 40’
please read the comments see how to download libtorch 1.3.1, or if possible, upgrade your pytorch to 1.6dev, or I believe 1.5 is fine.