Oh, interesting. It's the Wayward Cave (Main), using Method J. I've had no problems anywhere else so far. And it's odd that the ROM might be wrong.
I don't remember all the trials exactly but I do remember that the cave itself, for whatever reason, always advances the frame by 2. On three separate occasions, I hit my seed and sweet scented, sometimes immediately, other times waiting around 1 minute.
I expected to land on frame 3 (1 roamer), but I have landed on frame 5. Furthermore, the pokemon I caught all three times were Bronzors, when they should have been Zubats. The nature and IVs all match up. I then tried a few more times with different spreads and different frames, and the IVs all workout but the Encounter Slot itself was wrong on 5 separate occasions.
Odd, well for one thing, I'm fairly certain slot 3 is Bronzor and not Zubat at this point haha. I'd have to do the rest manually.