Hi,
You can find the customized files in the subfolders of the folder templates/YOUR_TEMPLATE/html/com_hikashop/ that you can access via FTP.
There, you have the product folder which contains the different files relative to the product layout customization, and the vote folder which contains the different files relative to the vote system customizations.
Rename the files there one by one in order to identify which files generates the problem.
Once you've identified the file, compare it to its equivalent in the core of HikaShop, in the folder components/com_hikashop/views/product/tmpl/ with a software like winmerge.
That way, you'll be able to see what is different and you can potentially test to replace the changes, one by one in the file