Resource Leveling using Shift Calendars

Hi,

I'm trying to level on resource on 3100 activity maintenance schedule.  The issue I'm seeing is around using Shift Calendars.  I see very different leveling results when there is a shift calendar assigned to the resource being leveled.  In particular, the leveler seems to leave large gaps or periods of inactivity in the resulting leveled activities for the resource. 

If I remove the shift calendar from the resource, the leveling looks good and has no inactivity gaps.

The shift calendar is 2-12 shifts.  When I assign it, for simplicity, I'm allocating 10h/h max/units for both shift 1 and the same for shift 2.