WP Casa Plugin has started duplicating content

I’m using the WP Casa property plugin to add property listings to my site. It’s worked fine for ages and all of a sudden it’s started adding the content into the post twice. The duplicated content appears above the correct content and the formatting is all over the place. I’ve been disabling plugins and can’t find any conflicts or anything to cause this! The strange thing is if I revert to 2016 default theme the problem doesn’t occur – any ideas please?