http://www.himeworks.com/2013/03/scene-interpreter/
For example, you use an item in the item menu, and any common events will be run in the item menu.
I was using one of the luna engine samples to make a screenshot but realized common events do not run in the item menu.
Then I found out it was this:
Line 4090 in Menu Luna of Etrian project
alias menu_luna_update update def update menu_luna_update @menu_status.update endNow, this doesn't actually call the superclass' update method for some reason.I'm not exactly sure why, but when I did this
alias menu_luna_update update def update super @menu_status.update endIt worked.

It might have broke other things in the process (I don't know, it might be aliasing something), so further investigation is required
To test the script,
1. Create a common event. Add this comment in the first line
<run scene: current>Then show a text message2. Set the potion to call this common event
3. Use the potion on an actor in the item menu
The problem can be resolved in several ways
- replace the alias with a super
- place the scene interpreter above the menu system (to force alias ordering)
To me, the more correct way is to provide a super call.