OnDragDetected doesn't detect on MouseButtonDown

I have widget class: W_SlotField. It generates slot of inventory. I also have InventoryHUD with Canvas as parent layer. In this Canvas I have one W_SlotField named INVENTORY, and Widget Switcher (also it can be horizontal box, border etc.), where I placed second W_SlotField named LOOT. By some reason items from INVENTORY field can be dragged, but items from LOOT field can’t be dragged.But in both cases, DetectDragEvent is called and LMB is pressed. If I will place W_SlotField named LOOT in Canvas it will start work

This is InventoryHUD

This is MouseButtonDownEvent

This is OnDragEventDetected

348102-drag-detect-event.png

This prints when I drag something from Inventory Slots

348103-drag-from-inventory.png

This prints when I drag something from Loot Slots

348104-drag-from-loot.png

Hello! Just have checked that - everything is ok. What kind of logic is inside W_SlotField? Am I right that you define methods in Item widgets (not in container)?