I just uploaded small update that should fix a number of issues.
Bug fix: elevator levels sometimes won't finish, forcing you to restart them
Bug fix: inventory would sometimes display wrong icon
Bug fix: prevent issue where player 2 could finish the level without player 1, causing problems with Corby in the next level if you switch to single player mode.
Balancing: Arcade level 4 is now easier!
Balancing tweaks to some bosses, enemy damage, health etc.