Hi,
The issue I see on your link is that the width and height of the img tag are specified as attributes, and then in the CSS the height is forced but the width is not mentioned. Because of that, it uses the width of the img tag and you get the image distorded.
If I check on my end on a localhost website with the latest version of HikaShop, I don't have the width/height attributes set in the img tag and thus the problem doesn't happen. So I don't think it's linked to the update of your HikaShop.
So I suppose it's either some "optimization" system plugin adding these attributes to all the images on your website, or you have a template override of the show_block_img view file which specifies these attributes.
A simple solution is to just add such CSS:
img.hikashop_child_image {
width: auto;
}
That way, the browser will calculate the width automatically based on the height you specified in the CSS and keep the ratio of the image so that it's not distorded. You can add such CSS in your template CSS or in the CSS of HikaShop.