Hello wiser, thanks a lot for this wonderful mod. But there's a major game-breaking bug that I've noticed. It happens more often on other emulators than mGBA. It happens on mGBA too so its not an emulator specific bug.
When there's too much sprites on the screen (overworld) and you open and change the first party Pokemon, it corrupts the game and you start walking on buildings. It registers you being at other location so collisions and warp stuff gets offsetted too. Also I've noticed that it happens when I switch a small sprite Pokemon (like mudkip) to bigger sprite Pokemon (like rayquaza). My guess on this is, the mountain exit bug you've fixed on previous version happened because of this too. There's too much sprites on mountain's exit and it causes the bug. Moving the berries was a temporary solution and it worked. But this can happen everywhere in the game because new following pokemon can be spawned everywhere in the game, and when is is spawned where there's too much overworld sprites are shown, the game may get bugged. I don't have an idea on how to fix this, but checking the code of changing following pokemon on overworld might help. By the way, the bug is recreatable. I will post the steps when I'm available.