RAX50 Router QOS Settings Won't Save

I enabled QOS inorder to allow me to set the priority levels (Low-Highest) for my attached devices according to my useage. I set my lowest priorty devices to (Low) and my highest priorty attached devices to (High) and saved the settings each time. None of "my" priority levels have been saved. The Routers QOS randomly selects each attached devices priority and ignores my preference. Henceforth I disabled QOS! Is this a known issue? Thank you.