twentyeleve – showcase page template problems

I made some changes to the content of a page with the showcase template and it now seems to have lost its sidebar area. I had a showcase.php file in a child template which I deleted but the problem remains. I then copied over showcase.php , functions.php and style.css from another WP site where the showcase template works perfectly. All without effect.

I tried creating a new page with the showcase template but this shows the same problem.

This is the showcase page displaying incorrectly:
https://www.marionandpeter.com/group200/?page_id=215

This is how the page looked before I changed the main content:
https://www.marionandpeter.com/group1001/

Can anyone suggest what I can do to correct the problem other than restore the site from a backup ?
Thanks.

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