not sure about the low battery warning since i haven't had that to me before - i think that was a problem with older batches of the grip and can be fixed or replaced by Canon.
i fixed my 'creaky grip' problem by putting a folded-over piece of name card alongside the contact shaft during assembly. probably not something that the service center will be able to help you with, as it's due to a design flaw in the attachment mechanism.
Actually i face the problem whereby my batteries are fully charged but it shows that the battery is low on the camera. It's quite irritating especially when it scares me that i'm running out of batt especially when i'm shooting events.
My BG is the new one according to the canon website, the one with the Gold contacts.
Has anybody with this problem sent their BG back to canon before? If so, what did they do about it?