Deleting Associate ID from a plan step

Good afternoon,

I've been trying to delete the associate ID from a plan step, but the change just won't take. 

This is what happens:

• I enter a step in a plan that has an associate ID
• I delete the associate ID.  This removes the associate name from the step
• I click "save" and exit the step
• When I enter the step again, the associate ID and Associate Name is still there as if I made no change

I've noticed that the only way to delete the associate ID is to delete the ID, make another change to the step(changing a due date), and then click save.  This is the only way to get what I need.  Is this expected behavior?

Thanks in advance for any help/advice.