Your problem, and that of your brother, are common results when factory unauthorized mods are made. Some work, some don't, and when they do they often have undesired results.
Before doing any mod, you should check all of the reflectors to see what results others have had before doing the mod yourself.
However, in this case it appears you are entering the incorrect sequence of keys. If you join the Yaesu Reflector on Yahoo, you'll find the "fix" if you can call it that.