Sidebar admin reports incorrect number of widgets

My Appearance/Widgets page reports “You are using 5 widgets in the Sidebar1 sidebar.” but only 4 widgets are shown on the right side of the page. At some point when I added a widget to the sidebar it only partially got added, and now I can’t find the parts to clean up.

I have looked in the database to find where information about active widgets, or sidebar content is located, but I can’t find it. Can anyone tell me where to look for this information.

You can read more detail about the cause of my problem here: https://bit.ly/FrJuX