Getting error river:comment:group:default

Dear Friends,

I am using elgg 1.8.8 with cool theme and some custom plugins, I can see this error in the home page activity when users post in groups.

river:comment:group:default 

Please someone help me, where can be the problem or which plugin is causing problem? I need to fix this urgent please help me I would be thankful.

 Many thanks & 

Kindest regards