Joomla - 3.1.5
K2 - 2.6.7
You can check it at
link
(please be patient server works a little bit slowly)
You may enter words for example "report", "trends" and look at web console.
Otherwise, when you enter some other words like "optimize" "evaluates" everything works well.
I think that issue is in &format=raw because classic searching works well. (&format=html)
Thanks for help