Noticed recently when I am in the bash shell, if i type a command incorrectly I have been getting an error that is not part of the command I was entering, but one that seems to be from the shell not knowing how to respond to an incorrect command.
After doing some searching, I found that this appears to be a permissions issue after upgrading. By entering the following command repaired my issue: sudo chmod ugo+r /var/lib/command-not-found/commands.db*
All good now!