Same issue for me. It looks related to bluetooth. If you plug in the keyboard, it goes away. I removed and re-added my keyboard and the problem still exists.

Is apple or anyone monitoring these treads?

Thanks! Worked for me as well

Fixed by going into recovery mode and unlocking the startup disk. Problem seems related to encrypted volumes.

Same problem. Related to encrypted volume. Reboot into recovery mode, select your startup disk unlock it with your password. Once it restarts, then you can upgrade again.