The first time a value is chosen from my dropdownlist it will display "object Object". After selecting an item a second time, it correctly displays. I've tracked the offending line down to binder.js:
isObservableObject = this._valueIsObservableObject
The first time through it is incorrectly (?) marked as an observable object so a complex object is set as the value.
Changing POA for an item that is not null works. Changing POA for the empty line shows object Object.