Hi,
Characteristics are still working fine on our end with the latest version of HikaShop, so I can only think that this issue comes from something that has been modified on your end.
Try to switch temporarily to the default template of Joomla. If it works with it, then it's likely that it comes from view overrides of your template.
In that case, try renaming the files under the folder templates/YOUR_TEMPLATE/html/com_hikashop/product/ one by one via FTP in order to identify the one causing the problem. Then, take the modifications you had done in that file, and reapply them to the new version of the file via the menu Display>Views.
