Level activities with small duration (<1 hour)

Hi,

You might want to look at the "Max unit / time" on the resource which assigned to those activities.

See if the max unit/time still allow the resource to be executed on the same hour or not..

Regard,

MRE

check your resource calendar also 

Any software should handle resource leveling down to the minimum duration you can assign to an activity, you got to be missing something. I do not use P6 but see it can display 1/100 minutes.

Try checking Activity Duration Type.

http://www.qsarticle.com/activity-duration-types-in-primavera-project-planner-p6/

If the above does not works then I suggest trying with the following simple schedule from scratch and see what happens. One resource A and one resource B units are available. There are no activity links, very simple. Even if one second activities it should do it.

Good luck.