I have gotten power level 4 on the mansion level with two different characters and at lest five times between them and I still have not gotten the achievement. I have all other achievements. This seems to be the only one not working.

Also: It said I unlocked a skeleton outfit and it is not available on the selection screen. I tried moving the selector in every direction from the outside edge of the 3x3 grid, still no skeleton. Others have mentioned this one too.

EDIT: In the library, it says the only locked acheivement is the spike challenge level, but when I view all achievements is says it is the Mansion Maniac one that is locked. I tried doing both over again and still no achievement.