Hi,
In the file "administrator/components/com_hikamarket/classes/vendor.php", please replace in the function "frontSaveForm":
$status = true;
$oldVendor = null;
$fieldsClass = hikamarket::get('shop.class.field');
$vendor = $fieldsClass->getInput(array('vendor','plg.hikamarket.vendor'), $oldVendor);
By:
$fieldsClass = hikamarket::get('shop.class.field');
$vendorClass = hikamarket::get('class.vendor');
$status = true;
$oldVendor = $vendorClass->get($vendor_id);
$vendor = $fieldsClass->getInput(array('vendor','plg.hikamarket.vendor'), $oldVendor);
It will fix the problem with the classical file custom field.
Regards,