Hi Ofi,
I doubt it's coming from Hikashop.
The issue is with SP modules.
It was working fine with SP3, but not at all with SP 5.
From what I can see between the production URL and the staging one, the difference is that the classes to handle the mobile/desktop display are missing in the HTML of the div wrappers: The div with the hidden class next to the clearfix class (in the staging URL) is missing.
It seems to be a bug of SPPB new version, not with Hikashop (already checked with them).
Note that if I add manually the class sppb-hidden-xs it hides the image as expected. But doesn't work with sppb-hidden-md sppb-hidden-lg sppb-hidden-sm
Sandra