Is it part of the design? If not take it back and swap! I would keep because it makes your tama unique and uniqe tamas are more speicial than un uniuqe tamas because yours is the only one like it!
-Cat
PS: If you would like any morwe info please feel free 2 pm me!
Well my v2 tama had that prob. Try taking the back off and screwing it in harder. I think that prob is caused by the battery not having enough pressure on it.