When user Pepper Potts is trying to view the "to-dos" section of the Employee Service Center, she is seeing many errors:
The behavior described above is now a documented Problem (PRB), PRB1370325.
The workaround for this behavior is to make a small change to Script Include "hr_ActivitySetAJAX" on line 155:
if (!parentTable || !parentId)
By making the above modification to the Script Include, a validation check (which was not previously present) is put in place for when a user is assigned a task with a parent record they cannot read.