Updated mgba core today because the standalone also got updated. And now when i press “start” it also works as the “A” button, as if i’m pressing 2 buttons at the same time. Reverting to the previous version fixes this so it’s an issue with the new core.
There was an issue with B acting as turbo A and B at the same time, but I reported it and it was fixed quickly. If you update to a ca21f86 build it should be fine. I tested it just now with Aria of Sorrow and couldn’t reproduce Start doing A inputs on Windows at least.