Can't do something about the jerking mouse as it is a client thing (.68 and onwards got the jerking mouse on most scripts), will take a look at the tree issue.
Are you lagging? I ran this myself a few days ago and it was flawless. Misclicks happen a lot when you're lagging because the mouse has moved to the correct spot (on your screen) but in-game it still hasnt reached that point yet, if that makes sense. Try shutting down all your other stuff and get back to me. Otherwise I'll have to add a failsafe for that staircase too.