Topic on Extension talk:Lingo
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Correction - this does not actually fix the issue. It DOES allow VisualEditor to open and work but the the site becomes unstable.
Further investigation revealed that (without the changes) VisualEditor opens up when you are CREATING a new page but pops an error when attempting to edit an existing page.
As a work-around, I simply open a new page and create my changes if needed then switch to Edit Source and copy pasta!