Hi,
this is not template issue,
links are based on current location and K2 (v.2.9) wasn't perfect written, so this kinds of differences are possible.
Check links from 2 areas:
DOMAIN
/berichte/herren6/itemlist/user/985-falkbernstein
DOMAIN/itemlist/user/985-falkbernstein
I guess you should ask creators of K2 why
or use 302 redirection to fix those issues.
