Right Ear Bud not charging in case

Hi - I own Jaybird Runs.

My right ear bud only seems to charge in the case, when I connect a USB to the case. The left ear bud is working perfectly. 

I have tried the cleaning tips, but this has not made a difference.

The situation is, that if I don't have my ear buds charging via a USB connection then the right ear bud's battery will drain and then be out of battery by the time I need to use again. 

It seems to be an issue, with the case rather than the right ear bud as when fully charged via the USB, there's no issues.

Appreciate any insight into this.

Thanks,
Tom