Facing issue on replacing chain

I am facing issue while replace chian, it's showng "Cannot replace chain: ... : The block last_hash must be correct" 
I've tried various way, but chain is not replacing with local chain.

Can you please review my code in github repo, my github repo is given bellow.
https://github.com/sajjadhira/blockchain-development-using-python-javascript-reactjs