Hi,
We checked again your server data, an regarding the function it should return the correct path.
What can cause this kind of error is, the live_site parameter in the Joomla config, but it seems to be correct, or it can be the canonical url, but it is correct too, in the votes, we use the function currentUrl too, so it should be working fine.
Another thing could be that you are using a SEF extension which potentially is adding alias to the url.
So if you have such extensions, thanks to disable it an try again.
Else thanks to provide us a backend and ftp access, you can send it via pm with the url of that topic.