Save display order not working after upgrade to 5.4.2.2

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I recently upgraded a client site to the latest version of C5 and since then the Save Display Order within Sets is not working for me. As a photographer, controlling the order of the images in galleries is important to him and having just added 30 new images to his gallery, the site looks a bit of a mess due to landscape & portrait images not being in the right order. Has anyone else seen this?

PassionForCreative