Write a quick powershell script to update the problem field, and the problem would go away . The change has to be made at the list level for it to take affect on existing pages/lists, but I believe making the modification to the column at the root web (or correct subweb) would work as well.
$web = $site.OpenWeb($site.RootWeb.ID)
$list = $web.Lists["Pages"]
[Microsoft.SharePoint.Publishing.Fields.HtmlField]$field = [Microsoft.SharePoint.Publishing.Fields.HtmlField]$list.Fields.GetFieldByInternalName("Abst ract")
$field.RichText = $true
$field.RichTextMode = [Microsoft.SharePoint.SPRichTextMode]::FullHtml
$field.Update()
$list.Update()
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