Sorry about that, it's a bug everyone is experiencing (I contacted the developer of the engine and they said the problem was in the engine, but someone is trying to fix it for me). It doesn't hinder you from reaching the end of the game, though, because the only items you need to combine can all be combined in the game screen, and if you mess up the character will just throw away the useless one and do it again.
Thanks for playing, and for the kind words!