Events thumbnails on homepage

hi,

I can't figure out why all pictures in the k2 items dissapear.
It happens always:
a) After simply changing the text in the demo events
b) Creating a new event and uploading a new picture

I changed the category-names of course.

the site: http://relaunch2015.indiadancedays.de/

thanks for your help

hello?
could some get back to me?

thanks in advance

Hi

I can see all images at the moment, so I think it can be related with cache. Can You please guide me step by step of what to do to replicate the issue ?