Key Value changes but the Task Doesn't stop until over.

I have a system where when I right click on a tree all selected units walk over to the tree and start chopping it down. I want it to be able to switch targets when I right click on a new tree but the AI wont move or do anything at all until its done chopping down the original tree. What can I do? I’ve tried changing the sequence to restart when the key value changes and switching the Observer aborts to self and neither of those work. I’m stumped.