For example they put Attack Attack! (Which should be labeled as emo, obviously) into metal category, as well as Asking Alexandria. Post-hardcore is not metal!!!
Also, the smaller things, like Suicide Silence is not death metal, it's deathcore, Terrorhorse is not thrash metal, it's death metal, some -core bands are labeled as something else etc.
This would not be so annoying for others but for example I get hugely annoyed when somebody calls bands like BFMV thrash metal. I would like the charting groups to do a little more research on genres before they put the songs to RBN.