There's a clue of the "New Feature" on my Youtube channel. Just put the pieces together. There will be also be an option not to use that feature is you prefer the old way.
Struggle was put in its moveset based on the Gen 4 move "Last resort". Looking at it now, that wasn't such a good idea. Umbreon just has a bad move ID, "Nothing" is just a placeholder to prevent glitch moves from happening just in case, so I'll fix that up in the next update. I won't be able to increase the bag/item storage size because of the RAM limitations of Gameboy. Gold's engine writes the ram in a more organized way, so that's why it can allow more packs.