After a while (15 min) the Listeners page hangs.
I tried several pc's with windows 10 and 7 but get the same problem.

Can you solve that?

Check this article out:

http://www.centova.com/en/faq/cast3/troubleshooting/centova_cast_statistics_pages_load_slowly_or_time_out

I had that happen to me once and was a pretty easy fix.