Hi shekharendu7.
I'm not sure what is causing this issue, but I've found a resolve.
I previously had Avast installed, and allowed the Avast One installer to upgrade / overwrite it. It was after I had done this when the smart scan began hanging up on stage 3 (83%).
I've just uninstalled Avast completely and done a fresh install from scratch. The smart scanner is working fine now. I’m guessing this issue occurs if you upgrade from Avast to Avast One.
I hope this helps.