Steps to reproduce:

• Create an article
• Copy a table from Google Spreadsheet
• Paste in RichText
• Publish

Results:
It's impossible to publish. Error message:
Summary Validation of XML content failed: Error in 40:0: Element section has extra content: para

Update 2020-06-04: Something very similar is still happening in some cases. https://ezcommunity.slack.com/archives/C3YFR5ZM4/p1591268321188600

When pasting anything (i.e.: a single word in plain text) in the editor, something (i'm guessing some javascript), adds the prefix http:// to all the internal links of the richtext.
So all internal links becomes something like: http://ezlocation://1952 .
If you take the time to remove the prefix from all internal links, the document validates and the content is saved.