Thanks, I hadn't noticed there was an update. I've now updated and the issue is resolved. Looking at the release notes I believe this was the issue:
Fix: Images with empty class not lazy loading
Because that image didn't have a class.
We're no longer using a carousel for that section, so the issue seems to be resolved, but if it helps the affected images were images that were used in an Owl Carousel.
I am however still having an issue where a particular image is not appearing at all when Smush CDN is enabled (with or without lazy loading). Specifically under the "Our Work" section of the homepage, there should be a logo image appearing on top of the black strip. Any help with that would be appreciated.
Thanks Kasia, it looks like I also needed to make sure that the semi-colon was present, as it didn't work without that either.
Also in regards to background images, they're being correctly optimised, but don't appear to be deferred when lazy loading is enabled. Is it correct that lazy loading of background images is not currently supported?
Lastly, I wanted to ask about <picture> elements again. We have a section where there's separate images for mobile and desktop, but when each is hidden for the other's screen size using only CSS, the image is still downloaded. The solution, as I understand it, is to use the picture element, however it doesn't appear to be supported by this plugin. Are there plans to add support? Or another method you suggest?