all images converted but some do not show

Dear Bjørn @roselldk

I have updated the plugin from github.
After checking the results I found that in some cases the webp images do not show up.
Below is the code of two images from the same page.
The first image is loaded as webp, the second appears as jpeg (using chrome).
As you can see there are some differences in the html code.
Most notably the source tag of the second (not loading) image has data-srcset attribute instead of srcset.

<picture>
<source srcset="komfort-2.jpg.webp 890w, komfort-2-300x192.jpg.webp 300w, komfort-2-768x493.jpg.webp 768w, komfort-2-20x13.jpg.webp 20w, komfort-2-600x385.jpg.webp 600w" sizes="(max-width: 890px) 100vw, 890px" type="image/webp">
<img width="890" height="571" src="komfort-2.jpg" class="vc_single_image-img attachment-full webpexpress-processed" alt="fűtőpanel működése" srcset="komfort-2.jpg 890w, komfort-2-300x192.jpg 300w, komfort-2-768x493.jpg 768w, komfort-2-20x13.jpg 20w, komfort-2-600x385.jpg 600w" sizes="(max-width: 890px) 100vw, 890px" data-dt-location="/komfort-2/">
</picture>

<picture>
<source data-srcset="x.jpg.webp 500w, x-300x151.jpg.webp 300w, x-20x10.jpg.webp 20w" sizes="(max-width: 500px) 100vw, 500px" type="image/webp">
<img width="500" height="251" src="x.jpg" class="lazy-load vc_single_image-img attachment-full webpexpress-processed is-loaded" alt="rx fűtőelem" sizes="(max-width: 500px) 100vw, 500px" data-dt-location="/x/" srcset="x.jpg 500w, x-300x151.jpg 300w, x-20x10.jpg 20w" style="will-change: auto;">
</picture>

I have checked the uploads folder and all webp versions for both images are there and they can be opened in browser too.
Can you please help me to find out what causes this?

Thank you very much indeed.

Best regards,
Endre