At seemingly random times, the option in the Gameplay section of the Options menu named "Enable Monster Power Selection" will reset or uncheck itself and therefore disable Monster Power Selection, hiding it from view in the Change Quest menu.
It has happened nearly every time i play a solo game on Monster Power 0, upon exiting it deactivates itself. It even does this when you Do use Monster Power.
While this is not a huge, gameplay altering bug, it is indeed annoying as each time you must go back into the Options and re-enable Monster Power Selection everytime. And I have personally tested whether relogging in, or rebooting Diablo 3 fixes this, but i've found this bug many times over the last 3 days.
I have no experience with hosting multiplayer games but i haven't noticed it happening after going into multiplayer. In terms of recreating this bug for the purpose of observation, but i do know it happens after leaving a solo or private game, but in terms of what i did in a clear step-to-step format is this:
1. I logged in, and changed the MP to 3, and the quest to act 1, the final quest.
2. I went hunting for an elite pack for a few minutes to ten, and afterwards i simply went into town.
3. Upon arriving in town, all i did was leave the game.
4. And Upon arriving at the Menu screen for your character (The Main Menu i guess?) i went to change the Monster Power to 0, but found it deactivated, despite having it activated earlier.
I know screenshots would not help, but even if i cannot make a video, I hope this was enough info, though i am willing to answer any and all questions.
Thank You for your time.