Diamonds falling out of platinum wedding band

Bought my fianc? a platinum diamond ring for R25 000<br> For our wedding on 3 October 2015.<br> On 24 December one of the diamonds fell out.<br> I returned the ring to browns and they fixed it.<br> On 29 February, the same diamond fell out again,<br> I took it back and this time the refused to fix unless I pay R1 100.what I don't understand is why I am being<br> Charged for their manufacturer / workmanship default.<br> It is clear their stones are prone to falling as this had happened in a space of 2 months. They have reuse used to refund me or fix my ring at no cost to me. My husband does not do any manual rough work / with his hands. I am disgusted because there are a lot of cheaper options which I didn't choose as I thought Browns was a reputable jeweler. I paid a premium for what I thought would be good quality and they have not lived up to this promise . My insurance doesn't cover a manufacturer default.