Hi there,
first off the URL that is appearing twice is added by your Minify plugin – maybe it has a cache that needs clearing or can be reset ?
The LCP time is being measured against the featured image of the first product ( as listed under Largest Contentful Paint element ).
The images are being lazyloaded which is why the LCP has increased.
I am not sure why updating to 5.5 would affect this – as your using a Lazyloader plugin and not WordPresses lazy load feature.