Two possible issues:
I think you should mention in the tutorial that PausedUnits also have the duration of their buffs paused. This is critical if you script a spell and want the effect to stop when the buff goes away. That is otherwise a very convenient way of coding; because it will automatically stack with purge/dispel/etc.
(Check Funny Bunny's Egg Hunt for an example of a Pause+Buff bug. If you cast Shadow Egg Strike just before a minigame; the targeted player will lose like 150 eggs (over time) instead of 15)
As far as I know; items can slip through very small spaces. For instance; if you have a single line of trees diagonally aligned; the item check might let a unit pass through there. I'd check some adjacent locations with the item too.