Have the same issue. Using Velocity theme that came bundled with Visual Composer.
<div class="wpb_single_image wpb_content_element vc_align_center">
<div class="wpb_wrapper">
<img class=" vc_box_border_grey " src="" width="" height=""
alt="arch-2" />
</div>
</div>
I have one image that is rendering in a page created by VC and have checked the post data for that image and it is the same as all others.
Images placed without using the VC render perfectly.
Any solution?