Smart Battery Case Keeps Breaking

Hi:

Bought an Apple Smart Battery Case for my iPhone 6.

After about 6 months it quit working- wouldn't charge at all.

Apple Store replaced it.

8 months later it has partially quit working: will charge fully if I just plug in the case by itself, but will not charge at all if the iPhone 6 is within the case.

Does this ring any bells with anyone? Or is it just a quirk of the case that they break kind of often? Since it is now 14 months later, I am assuming Apple will no longer warranty it (I am assuming a 12 mo warranty but don't know for sure).

Any and all ideas appreciated. If out of warranty and Apple won't back it, any suggestions for OEM cases that are a bit more robust? Thanks!