Armed with that response, I returned to my tree and, sure enough, there was a citation that had been uploaded with the original gedcom that could be considered 'lengthy'.
Clicking the 'Edit Source' button took me to a screen where I could hopefully make some changes to shorten the citation.
I then scrolled to the bottom of the page to locate the button to save the source.
That's when I got the dreaded 'We're Sorry' page
I've tried editing the source multiple times and it always comes to this page.
So, now I'm playing with a 'test' tree to see what happens when I delete the source. If I click the View button for the source, the source window opens. On this window is a 'Remove' button
There is a limit to the length of a citation on Ancestry!
I have called Ancestry on this issue since I want to know what that limit is. The support person I reached had not seen this issue before. She was very thorough in reviewing the problem and discovered another, potentially related issue: The person's name could not be searched but was in the list of people. My case is being reviewed and hopefully, I will find out the maximum length for a citation.