No one else reported such issue so far and we've had already at least a few hundred merchants update their HikaShop. So I don't think that there is a problem with the update with HikaShop.
The error "Unable to find install package" is something displayed by the Joomla installer when it can't find the install package when you "upload and install" it. It can happen when you have access right issues with your folders, wrong tmp folder path in your Joomla configuration, etc. The install via FTP method completely circumvent that as the files to be installed are already available for the Joomla installer to run the install process, which is why I recommended it.