I have noticed in several games (one I run and two I play in) that the Passive Wisdom formula sometimes gets wonky.  Every other week or so I have to go into the Abilities tab and reset the value to accurately reflect the character's actual passive perception score.  Different games and different characters reset the value to different numbers as well. Sometimes it is 10+Wisdom Score, sometimes it is 20+Wisdom Modifier, sometimes it is something in between.   Any thoughts?