curious rigging question

hello blender artist, so lately ive been experimenting with rigging using nathan humane rigging dvd. i was rigging the finger using the action constraint which nathan shows. everything works fine the only question i have is when i duplicate the finger rig, the action constraint becomes broken. so i thought maybe it needs an update by perhaps exiting and reentering pose mode but that didnt seem to help. i also deleted the action constraint and reapply the constraint, but didnt seem to work either. has anyone came across this? im just curious cause when i duplicate the entire finger bone rig the copy rotation follow and is still linked but not the action constraint