Sorry to bump but just asking, are you using an Analogue Pocket? I had that issue that the Analogue doesn't save the gems at all, I could play the game, power off, reset, continue, power off, etc etc on a GBA or GBC and everything will be there but as soon as I take my cart with that save working and put it on the Analogue tobo play, as soon as it "saves" all my gems are gone, tested it multiple times and always happened the same, so if you are using the Analogue that's the problem, if not, well, there is something else going on that we need to find out.