As the chapter starts to launch press alt/f4. It will close the game. When you come back in, you will be able to launch the chapter. This worked for both my wife and me.
It would be a nice to get a reply or update. Silence doesn't help explain what is going on. We've taken a couple more toons through the entire set of star fortresses since I last posted this, and no bracer drops in any run.
Are the drops of these in Star Fortresses bugged or did the drop rate change with 4.x? We've done >15 of these on different characters over the last couple of weeks without a single bracers drop of any type. It seemed to change when the area loot change happened.