Stops responding and freezes on Saving World screen

After returning to Overworld from Nether, right click no longer works on an object (e.g. right click on a chest and nothing happens). I'm also not able to open my own inventory (pressing E doesn't do anything). Esc key does work and I click on Save & Exit button. Minecraft displays the "Saving World" dialog box and stays there. When I kill the game using task manager and re-load, it frequently puts me back in the nether. Sometimes the problem occurs again and other times it starts working normally again. This has happened a half dozen times in the last day since the upgrade to 1.16.100. Also, about a quarter of the time, it doesn't return me to the portal - it drops me below the portal - this is also a new problem since the update.