People Picker in Project Detail Pages - Not Working for Already Created Projects

Hi,

I have a non-mandatory field (say, "Expert") in PDP. When I create a new project, I can select the "Expert" using People Picker. When I try to open an existing project (to assign/reassign an "Expert") the People Picker feature does not work. Custom scripting is already activated. Any insight from users, as to what configuration changes should be made, would be much appreciated. 

Thanks