[WP Smush Pro] Issue with AWS Offload and Smush

Hi Guys,
Having an issue with the Smush plugin. When we activate it and AWS offload we get Warning: Illegal string offset 'filesize' in /home/forge/pri-stg.wtbidev.co.uk/public/wp-content/plugins/amazon-s3-and-cloudfront-pro/classes/amazon-s3-and-cloudfront.php on line 1125
12597
This only happens with doc, docx & pptx (so far). When your plugin is turned off it works fine.

Any ideas?