I had tried rebooting my server and it didn't fix the error - which leads me to believe that Hmwk Sets editor has a fixed seed that it uses to render the problems? If so, does anyone know what it is?
This post can be deleted. There was an error with problem #2, where the randomization allowed for the sum to be 1 (in this case, 3/6+3/6), rather than a proper fraction.