I've completed Portal training, so my modifiers are preserved for the same mission types. However, this feature partially stopped working since I hit 360 Power. Now whenever I select any customizable activity, the game forces me to do Grandmaster, even if I previously selected Master difficulty. Clip shows an example. I start an activity on Master, so I expect next time I select any activity, Master difficulty will be chosen. I ran through the mission, and once I open Portal to restart it, Grandmaster difficulty is selected! Changing difficulty also resets bane modifier, so I need to fix it, and only then I can start the activity again.