I know this is quite old, but I am having the same issue. Adding an image caption causes the fallback image to be loaded, and jquery does not switch images.
I have 3 media query formats:
all w300 (fallback image)
(min-width:420px) w552
(min-width:890px) w930
My screen is wider than 89opx.
When no image caption is present, this is how an image is rendered:
<span data-picture="" data-alt="some-alt-text" class="alignnone" data-width="1377" data-height="909">
<span data-src="https://website.com/slir/w300/wp-content/uploads/image.jpg" data-media="all"></span>
<span data-src="https://website.com/slir/w552/wp-content/uploads/image.jpg" data-media="(min-width:420px)"></span>
<noscript><img src="https://website.com/slir/w552/wp-content/uploads/image.jpg" class="alignnone" alt="some-alt-text" width="1377" height="909"></noscript>
<span data-src="https://website.com/slir/w930/wp-content/uploads/2015/03/image.jpg" data-media="(min-width:890px)"></span>
<img alt="Beni-and-Ioana" src="https://website.com/slir/w930/wp-content/uploads/image.jpg">
</span>
With caption:
<figure class="figure alignnone">
<img src="https://website.com/slir/w300/wp-content/uploads/image.jpg" alt="some-alt-text" width="1377" height="909"><figcaption>
<span data-src="https://website.com/slir/w930/wp-content/uploads/image.jpg" data-media="(min-width:890px)"></span> Caption Text</figcaption></figure>
<figcaption>
<span data-src="website.com/slir/w930/wp-content/uploads/image.jpg" data-media="(min-width:890px)"></span> Caption Text
</figcaption>
With caption, but without PB Responsive Images activated:
<figure class="figure alignnone">
<img src="https://website.com/wp-content/uploads/image.jpg" alt="some-alt-text" width="1377" height="909">
<figcaption>Caption Text</figcaption>
</figure>