If you have the account data you may have a look behind the scenes.
I did not set up the site, I just started to work on it. Plus I'm pretty new to joomla. So...not sure.
What I noticed now having a quick look is josetta - k2 items and josetta - k2 categories. Could those be "suspects"?

thanks

tried disabling the above: nothing changed.
If you could tell me which file(s) is responsible for getting that ajax request and storing a vote, maybe I could try to debug it by myself.