Drag & drop problem

I encountered a strange problem
I’m trying to make inventory with “drag and drop” according to tutorials, everything works as it should, but if you drag a widget from right to left, “On drop” event is called in the dragged widget, and not in the destination.
Attached the clip.
Sorry for my english.
https://www.youtube.com/watch?v=z-4LLyH4Eyc&ab_channel=EL