I think the problem is how I probe directories. I made a change regarding that recently that I knew might slow things down. I'll see about potentially backing it out.
E] Probably fixed with https://github.com/mgba-emu/mgba/commit/...0f504fb0d2, which will be in tomorrow's nightly.
E] Probably fixed with https://github.com/mgba-emu/mgba/commit/...0f504fb0d2, which will be in tomorrow's nightly.