Lesson 9. Drop event fires twice

[Paprikas]

I gues it is something with new versions of Vue handling @drop event differently.
Anyway, for those who stuck with double firing, here is the fix. Add .self modifier

<AppDrop @drop.self="moveTaskOrColumn"

Same for tasks and columns.

Read more https://vuejs.org/guide/essentials/event-handling.html#event-modifiers