A riverdashboard error of group discussion comments of Elgg 1.7

There is public group with enabled blog, enabled bookmarks, enabled files and  enabled group discussion.

I made a post and then 4 comments.

topic001,description001

description002

description003

description004

description005

The riverdashboard display something like these:

somebody, newtopic, topic001, description001

somebody, newcomment for topic001, description005

somebody, newcomment for topic001, description005

somebody, newcomment for topic001, description005

somebody, newcomment for topic001, description005

It is obviously an error. But this error never reprodue again.