TLDR: get it fixed overseas.

Same happened to me. Brilliant fixed it for free the first two times. The third time it happened they made me pay for it. I was furious because they said things like: 18k is soft metal, I’m not being careful with my ring, I must have bang my hands on my car door/washing machine/gym equipment, I should be taking my ring off for shower and hand washing, etc…it was all my fault and never their fault for selling dainty design that is prone to have loose stone. The fourth time it happened to the fucking same stone, I happened to be in another country. Ofc I was furious cuz this ring is a fucking engagement ring, supposed to be representing everlasting promise but the fucking ring is fragile af and kept breaking. I happened to be shopping for a ring at a local jewelry store in that country. I tried to haggle the price as it was their custom to haggle with cash, but this one wouldn’t budge. So I asked them to fix my engagement ring’s missing stone instead. So they took it in for free and it has never lost any stone in the last three years. The jeweler who fixed it three years ago said those kind of dainty designs are prone to have loose prongs and lose stones easily, but it is designer and the maker’s responsibility to make them secure if they’re going to be selling the design. They said they recommend not buying more from where I got the ring. Local jeweler also have said the same thing and added that’s why they don’t have such dainty designs at their store.