WordPress 4.4 and lazysizes?

Hello everyone,

I used to use lazysizes js (aFarkas/lazysizes @ https://github.com/aFarkas/lazysizes) to delay the loading of the image.

However, after the wordpress 4.4, it seems some of my images don’t lazy load anymore.
Also, some images are loaded as original size image as supposed to smaller resolution.

I’ve heard that the wp4.4 incorporates a responsive image feature, is this conflict with lazysizes plugin?

Thanks a lot.

Happy Holiday.